src/Mvc/Mvc.DataAnnotations/test/DataAnnotationsMetadataProviderTest.cs - main - githubmirror/aspnetcore

src/Mvc/Mvc.DataAnnotations/test/DataAnnotationsMetadataProviderTest.cs
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Remove long-obsolete MVC APIs targeted for removal (#67077)
24 июн 2026, 18:18
24 июн 2026, 18:18ae22b8b
// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.

using System.ComponentModel;
using System.ComponentModel.DataAnnotations;
using System.Globalization;

using Microsoft.AspNetCore.Mvc.ModelBinding;
using Microsoft.AspNetCore.Mvc.ModelBinding.Metadata;
using Microsoft.AspNetCore.Mvc.ModelBinding.Validation;
using Microsoft.AspNetCore.InternalTesting;
using Microsoft.Extensions.Localization;
using Microsoft.Extensions.Options;
using Moq;

namespace Microsoft.AspNetCore.Mvc.DataAnnotations;

public enum TestEnum
{
    [Display(Name = "DisplayNameValue")]
    DisplayNameValue
}

public class DataAnnotationsMetadataProviderTest
{
    // Includes attributes with a 'simple' effect on display details.
    public static TheoryData<object, Func<DisplayMetadata, object>, object> DisplayDetailsData
    {
        get
        {
            return new TheoryData<object, Func<DisplayMetadata, object>, object>
                {
                    { new DataTypeAttribute(DataType.Duration), d => d.DataTypeName, DataType.Duration.ToString() },

                    { new DisplayAttribute() { Description = "d" }, d => d.Description(), "d" },
                    { new DisplayAttribute() { Name = "DN" }, d => d.DisplayName(), "DN" },
                    { new DisplayAttribute() { Order = 3 }, d => d.Order, 3 },
                    { new DisplayAttribute() { Prompt = "Enter Value" }, d => d.Placeholder(), "Enter Value" },

                    { new DisplayColumnAttribute("Property"), d => d.SimpleDisplayProperty, "Property" },

                    { new DisplayFormatAttribute() { ConvertEmptyStringToNull = true }, d => d.ConvertEmptyStringToNull, true },
                    { new DisplayFormatAttribute() { DataFormatString = "{0:G}" }, d => d.DisplayFormatString, "{0:G}" },
                    {
                        new DisplayFormatAttribute() { DataFormatString = "{0:G}" },
                        d => d.DisplayFormatStringProvider(),
                        "{0:G}"
                    },
                    {
                        new DisplayFormatAttribute() { DataFormatString = "{0:G}", ApplyFormatInEditMode = true },
                        d => d.EditFormatString,
                        "{0:G}"
                    },
                    {
                        new DisplayFormatAttribute() { DataFormatString = "{0:G}", ApplyFormatInEditMode = true },
                        d => d.EditFormatStringProvider(),
                        "{0:G}"
                    },
                    {
                        new DisplayFormatAttribute() { DataFormatString = "{0:G}", ApplyFormatInEditMode = true },
                        d => d.HasNonDefaultEditFormat,
                        true
                    },
                    { new DisplayFormatAttribute() { HtmlEncode = false }, d => d.HtmlEncode, false },
                    { new DisplayFormatAttribute() { NullDisplayText = "(null)" }, d => d.NullDisplayText, "(null)" },
                    {
                        new DisplayFormatAttribute() { NullDisplayText = "(null)" },
                        d => d.NullDisplayTextProvider(),
                        "(null)"
                    },

                    { new DisplayNameAttribute("DisplayNameValue"), d => d.DisplayName(), "DisplayNameValue"},
                    { new HiddenInputAttribute() { DisplayValue = false }, d => d.HideSurroundingHtml, true },

                    { new ScaffoldColumnAttribute(scaffold: false), d => d.ShowForDisplay, false },
                    { new ScaffoldColumnAttribute(scaffold: false), d => d.ShowForEdit, false },

                    { new UIHintAttribute("hintHint"), d => d.TemplateHint, "hintHint" },
                };
        }
    }

    [Theory]
    [MemberData(nameof(DisplayDetailsData))]
    public void CreateDisplayMetadata_SimpleAttributes(
        object attribute,
        Func<DisplayMetadata, object> accessor,
        object expected)
    {
        // Arrange
        var provider = CreateProvider();

        var key = ModelMetadataIdentity.ForType(typeof(string));
        var context = new DisplayMetadataProviderContext(key, GetModelAttributes(new object[] { attribute }));

        // Act
        provider.CreateDisplayMetadata(context);

        // Assert
        var value = accessor(context.DisplayMetadata);
        Assert.Equal(expected, value);
    }

    [Fact]
    public void CreateDisplayMetadata_FindsDisplayFormat_FromDataType()
    {
        // Arrange
        var provider = CreateProvider();

        var dataType = new DataTypeAttribute(DataType.Currency);
        var displayFormat = dataType.DisplayFormat; // Non-null for DataType.Currency.

        var attributes = new[] { dataType, };
        var key = ModelMetadataIdentity.ForType(typeof(string));
        var context = new DisplayMetadataProviderContext(key, GetModelAttributes(attributes));

        // Act
        provider.CreateDisplayMetadata(context);

        // Assert
        Assert.Same(displayFormat.DataFormatString, context.DisplayMetadata.DisplayFormatString);
    }

    [Fact]
    public void CreateDisplayMetadata_FindsDisplayFormat_OverridingDataType()
    {
        // Arrange
        var provider = CreateProvider();

        var dataType = new DataTypeAttribute(DataType.Time); // Has a non-null DisplayFormat.
        var displayFormat = new DisplayFormatAttribute() // But these values override the values from DataType
        {
            DataFormatString = "Cool {0}",
        };

        var attributes = new Attribute[] { dataType, displayFormat, };
        var key = ModelMetadataIdentity.ForType(typeof(string));
        var context = new DisplayMetadataProviderContext(key, GetModelAttributes(attributes));

        // Act
        provider.CreateDisplayMetadata(context);

        // Assert
        Assert.Same(displayFormat.DataFormatString, context.DisplayMetadata.DisplayFormatString);
    }

    [Fact]
    public void CreateBindingMetadata_EditableAttributeFalse_SetsReadOnlyTrue()
    {
        // Arrange
        var provider = CreateProvider();

        var editable = new EditableAttribute(allowEdit: false);

        var attributes = new Attribute[] { editable };
        var key = ModelMetadataIdentity.ForType(typeof(string));
        var context = new BindingMetadataProviderContext(key, GetModelAttributes(attributes));

        // Act
        provider.CreateBindingMetadata(context);

        // Assert
        Assert.True(context.BindingMetadata.IsReadOnly);
    }

    [Fact]
    public void CreateBindingMetadata_EditableAttributeTrue_SetsReadOnlyFalse()
    {
        // Arrange
        var provider = CreateProvider();

        var editable = new EditableAttribute(allowEdit: true);

        var attributes = new Attribute[] { editable };
        var key = ModelMetadataIdentity.ForType(typeof(string));
        var context = new BindingMetadataProviderContext(key, GetModelAttributes(attributes));

        // Act
        provider.CreateBindingMetadata(context);

        // Assert
        Assert.False(context.BindingMetadata.IsReadOnly);
    }

    [Fact]
    public void CreateDisplayMetadata_DisplayAttribute_OverridesDisplayNameAttribute()
    {
        // Arrange
        var provider = CreateProvider();

        var displayName = new DisplayNameAttribute("DisplayNameAttributeValue");
        var display = new DisplayAttribute()
        {
            Name = "DisplayAttributeValue"
        };

        var attributes = new Attribute[] { display, displayName };
        var key = ModelMetadataIdentity.ForType(typeof(string));
        var context = new DisplayMetadataProviderContext(key, GetModelAttributes(attributes));

        // Act
        provider.CreateDisplayMetadata(context);

        // Assert
        Assert.Equal("DisplayAttributeValue", context.DisplayMetadata.DisplayName());
    }

    [Fact]
    public void CreateDisplayMetadata_DisplayAttribute_OverridesDisplayNameAttribute_IfNameEmpty()
    {
        // Arrange
        var provider = CreateProvider();

        var displayName = new DisplayNameAttribute("DisplayNameAttributeValue");
        var display = new DisplayAttribute()
        {
            Name = string.Empty
        };

        var attributes = new Attribute[] { display, displayName };
        var key = ModelMetadataIdentity.ForType(typeof(string));
        var context = new DisplayMetadataProviderContext(key, GetModelAttributes(attributes));

        // Act
        provider.CreateDisplayMetadata(context);

        // Assert
        Assert.Equal(string.Empty, context.DisplayMetadata.DisplayName());
    }

    [Fact]
    public void CreateDisplayMetadata_DisplayAttribute_DoesNotOverrideDisplayNameAttribute_IfNameNull()
    {
        // Arrange
        var provider = CreateProvider();

        var displayName = new DisplayNameAttribute("DisplayNameAttributeValue");
        var display = new DisplayAttribute()
        {
            Description = "This is a description"
        };

        var attributes = new Attribute[] { display, displayName };
        var key = ModelMetadataIdentity.ForType(typeof(string));
        var context = new DisplayMetadataProviderContext(key, GetModelAttributes(attributes));

        // Act
        provider.CreateDisplayMetadata(context);

        // Assert
        Assert.Equal("DisplayNameAttributeValue", context.DisplayMetadata.DisplayName());
    }

    [Fact]
    public void CreateDisplayMetadata_DisplayNameAttribute_OnEnum_CompatShimOn()
    {
        // Arrange
        var sharedLocalizer = new Mock<IStringLocalizer>(MockBehavior.Strict);
        sharedLocalizer
            .Setup(s => s["DisplayNameValue"])
            .Returns(new LocalizedString("DisplayNameValue", "Name from DisplayNameAttribute"));

        var stringLocalizerFactoryMock = new Mock<IStringLocalizerFactory>(MockBehavior.Strict);
        stringLocalizerFactoryMock
            .Setup(s => s.Create(typeof(EmptyClass)))
            .Returns(() => sharedLocalizer.Object);

        var localizationOptions = new MvcDataAnnotationsLocalizationOptions();
        localizationOptions.DataAnnotationLocalizerProvider = (type, stringLocalizerFactory) =>
        {
            return stringLocalizerFactory.Create(typeof(EmptyClass));
        };

        var provider = CreateProvider(options: null, localizationOptions, stringLocalizerFactoryMock.Object);

        var displayName = new DisplayNameAttribute("DisplayNameValue");

        var attributes = new Attribute[] { displayName };
        var key = ModelMetadataIdentity.ForType(typeof(TestEnum));
        var context = new DisplayMetadataProviderContext(key, GetModelAttributes(attributes));

        // Act
        provider.CreateDisplayMetadata(context);

        // Assert
        Assert.Collection(context.DisplayMetadata.EnumGroupedDisplayNamesAndValues, (e) =>
        {
            Assert.Equal("Name from DisplayNameAttribute", e.Key.Name);
        });
    }

    [Fact]
    public void CreateDisplayMetadata_DisplayNameAttribute_LocalizesDisplayName()
    {
        // Arrange
        var sharedLocalizer = new Mock<IStringLocalizer>(MockBehavior.Strict);
        sharedLocalizer
            .Setup(s => s["DisplayNameValue"])
            .Returns(new LocalizedString("DisplayNameValue", "Name from DisplayNameAttribute"));

        var stringLocalizerFactoryMock = new Mock<IStringLocalizerFactory>(MockBehavior.Strict);
        stringLocalizerFactoryMock
            .Setup(s => s.Create(typeof(EmptyClass)))
            .Returns(() => sharedLocalizer.Object);

        var localizationOptions = new MvcDataAnnotationsLocalizationOptions();
        localizationOptions.DataAnnotationLocalizerProvider = (type, stringLocalizerFactory) =>
        {
            return stringLocalizerFactory.Create(typeof(EmptyClass));
        };

        var provider = CreateProvider(options: null, localizationOptions, stringLocalizerFactoryMock.Object);

        var displayName = new DisplayNameAttribute("DisplayNameValue");

        var attributes = new Attribute[] { displayName };
        var key = ModelMetadataIdentity.ForType(typeof(string));
        var context = new DisplayMetadataProviderContext(key, GetModelAttributes(attributes));

        // Act
        provider.CreateDisplayMetadata(context);

        // Assert
        Assert.Equal("Name from DisplayNameAttribute", context.DisplayMetadata.DisplayName());
    }

    [Fact]
    public void CreateDisplayMetadata_DisplayAttribute_NameFromResources_UsesDataAnnotationLocalizerProvider()
    {
        // Arrange
        var sharedLocalizer = new Mock<IStringLocalizer>(MockBehavior.Loose);

        var stringLocalizerFactoryMock = new Mock<IStringLocalizerFactory>(MockBehavior.Strict);
        stringLocalizerFactoryMock
            .Setup(s => s.Create(typeof(EmptyClass)))
            .Returns(() => sharedLocalizer.Object);

        var localizationOptions = new MvcDataAnnotationsLocalizationOptions();
        var dataAnnotationLocalizerProviderWasUsed = false;
        localizationOptions.DataAnnotationLocalizerProvider = (type, stringLocalizerFactory) =>
        {
            dataAnnotationLocalizerProviderWasUsed = true;
            return stringLocalizerFactory.Create(typeof(EmptyClass));
        };

        var provider = CreateProvider(options: null, localizationOptions, stringLocalizerFactoryMock.Object);

        var display = new DisplayAttribute()
        {
            Name = "DisplayName"
        };

        var attributes = new Attribute[] { display };
        var key = ModelMetadataIdentity.ForType(typeof(string));
        var context = new DisplayMetadataProviderContext(key, GetModelAttributes(attributes));

        // Act
        provider.CreateDisplayMetadata(context);
        context.DisplayMetadata.DisplayName();

        // Assert
        Assert.True(dataAnnotationLocalizerProviderWasUsed, "DataAnnotationLocalizerProvider wasn't used by DisplayMetadata");
    }

    // This is IMPORTANT. Product code needs to use GetName() instead of .Name. It's easy to regress.
    [Fact]
    public void CreateDisplayMetadata_DisplayAttribute_NameFromResources_NullLocalizer()
    {
        // Arrange
        var provider = CreateProvider();

        var display = new DisplayAttribute()
        {
#if USE_REAL_RESOURCES
                Name = nameof(Test.Resources.DisplayAttribute_Name),
                ResourceType = typeof(Test.Resources),
#else
            Name = nameof(DataAnnotations.Test.Resources.DisplayAttribute_Name),
            ResourceType = typeof(TestResources),
#endif
        };

        var attributes = new Attribute[] { display };
        var key = ModelMetadataIdentity.ForType(typeof(string));
        var context = new DisplayMetadataProviderContext(key, GetModelAttributes(attributes));

        // Act
        provider.CreateDisplayMetadata(context);

        // Assert
        Assert.Equal("name from resources", context.DisplayMetadata.DisplayName());
    }

    // This is IMPORTANT. Product code needs to use GetName() instead of .Name. It's easy to regress.
    [Fact]
    public void CreateDisplayMetadata_DisplayAttribute_NameFromResources_WithLocalizer()
    {
        // Arrange
        // Nothing on stringLocalizer should be called
        var stringLocalizer = new Mock<IStringLocalizer>(MockBehavior.Strict);
        var stringLocalizerFactory = new Mock<IStringLocalizerFactory>();
        stringLocalizerFactory
            .Setup(s => s.Create(It.IsAny<Type>()))
            .Returns(() => stringLocalizer.Object);
        var provider = CreateProvider(stringLocalizerFactory: stringLocalizerFactory.Object);

        var display = new DisplayAttribute()
        {
#if USE_REAL_RESOURCES
                Name = nameof(Test.Resources.DisplayAttribute_Name),
                ResourceType = typeof(Test.Resources),
#else
            Name = nameof(DataAnnotations.Test.Resources.DisplayAttribute_Name),
            ResourceType = typeof(TestResources),
#endif
        };

        var attributes = new Attribute[] { display };
        var key = ModelMetadataIdentity.ForType(typeof(string));
        var context = new DisplayMetadataProviderContext(key, GetModelAttributes(attributes));

        // Act
        provider.CreateDisplayMetadata(context);

        // Assert
        Assert.Equal("name from resources", context.DisplayMetadata.DisplayName());
    }

    // This is IMPORTANT. Product code needs to use GetDescription() instead of .Description. It's easy to regress.
    [Fact]
    public void CreateDisplayMetadata_DisplayAttribute_DescriptionFromResources_WithLocalizer()
    {
        // Arrange
        // Nothing on stringLocalizer should be called
        var stringLocalizer = new Mock<IStringLocalizer>(MockBehavior.Strict);
        var stringLocalizerFactory = new Mock<IStringLocalizerFactory>();
        stringLocalizerFactory
            .Setup(s => s.Create(It.IsAny<Type>()))
            .Returns(() => stringLocalizer.Object);
        var provider = CreateProvider(stringLocalizerFactory: stringLocalizerFactory.Object);

        var display = new DisplayAttribute()
        {
#if USE_REAL_RESOURCES
                Description = nameof(Test.Resources.DisplayAttribute_Description),
                ResourceType = typeof(Test.Resources),
#else
            Description = nameof(DataAnnotations.Test.Resources.DisplayAttribute_Description),
            ResourceType = typeof(TestResources),
#endif
        };

        var attributes = new Attribute[] { display };
        var key = ModelMetadataIdentity.ForType(typeof(string));
        var context = new DisplayMetadataProviderContext(key, GetModelAttributes(attributes));

        // Act
        provider.CreateDisplayMetadata(context);

        // Assert
        Assert.Equal("description from resources", context.DisplayMetadata.Description());
    }

    // This is IMPORTANT. Product code needs to use GetDescription() instead of .Description. It's easy to regress.
    [Fact]
    public void CreateDisplayMetadata_DisplayAttribute_DescriptionFromResources_NullLocalizer()
    {
        // Arrange
        var provider = CreateProvider();

        var display = new DisplayAttribute()
        {
#if USE_REAL_RESOURCES
                Description = nameof(Test.Resources.DisplayAttribute_Description),
                ResourceType = typeof(Test.Resources),
#else
            Description = nameof(DataAnnotations.Test.Resources.DisplayAttribute_Description),
            ResourceType = typeof(TestResources),
#endif
        };

        var attributes = new Attribute[] { display };
        var key = ModelMetadataIdentity.ForType(typeof(string));
        var context = new DisplayMetadataProviderContext(key, GetModelAttributes(attributes));

        // Act
        provider.CreateDisplayMetadata(context);

        // Assert
        Assert.Equal("description from resources", context.DisplayMetadata.Description());
    }

    // This is IMPORTANT. Product code needs to use GetPrompt() instead of .Prompt. It's easy to regress.
    [Fact]
    public void CreateDisplayMetadata_DisplayAttribute_PromptFromResources_WithLocalizer()
    {
        // Arrange
        // Nothing on stringLocalizer should be called
        var stringLocalizer = new Mock<IStringLocalizer>(MockBehavior.Strict);
        var stringLocalizerFactory = new Mock<IStringLocalizerFactory>();
        stringLocalizerFactory
            .Setup(s => s.Create(It.IsAny<Type>()))
            .Returns(() => stringLocalizer.Object);
        var provider = CreateProvider(stringLocalizerFactory: stringLocalizerFactory.Object);

        var display = new DisplayAttribute()
        {
#if USE_REAL_RESOURCES
                Prompt = nameof(Test.Resources.DisplayAttribute_Prompt),
                ResourceType = typeof(Test.Resources),
#else
            Prompt = nameof(DataAnnotations.Test.Resources.DisplayAttribute_Prompt),
            ResourceType = typeof(TestResources),
#endif
        };

        var attributes = new Attribute[] { display };
        var key = ModelMetadataIdentity.ForType(typeof(string));
        var context = new DisplayMetadataProviderContext(key, GetModelAttributes(attributes));

        // Act
        provider.CreateDisplayMetadata(context);

        // Assert
        Assert.Equal("prompt from resources", context.DisplayMetadata.Placeholder());
    }

    // This is IMPORTANT. Product code needs to use GetPrompt() instead of .Prompt. It's easy to regress.
    [Fact]
    public void CreateDisplayMetadata_DisplayAttribute_PromptFromResources_NullLocalizer()
    {
        // Arrange
        var provider = CreateProvider();

        var display = new DisplayAttribute()
        {
#if USE_REAL_RESOURCES
                Prompt = nameof(Test.Resources.DisplayAttribute_Prompt),
                ResourceType = typeof(Test.Resources),
#else
            Prompt = nameof(DataAnnotations.Test.Resources.DisplayAttribute_Prompt),
            ResourceType = typeof(TestResources),
#endif
        };

        var attributes = new Attribute[] { display };
        var key = ModelMetadataIdentity.ForType(typeof(string));
        var context = new DisplayMetadataProviderContext(key, GetModelAttributes(attributes));

        // Act
        provider.CreateDisplayMetadata(context);

        // Assert
        Assert.Equal("prompt from resources", context.DisplayMetadata.Placeholder());
    }

    [Fact]
    public void CreateDisplayMetadata_DisplayAttribute_LocalizeProperties()
    {
        // Arrange
        var stringLocalizer = new Mock<IStringLocalizer>(MockBehavior.Strict);
        stringLocalizer
            .Setup(s => s["Model_Name"])
            .Returns(() => new LocalizedString("Model_Name", "name from localizer " + CultureInfo.CurrentCulture));
        stringLocalizer
            .Setup(s => s["Model_Description"])
            .Returns(() => new LocalizedString("Model_Description", "description from localizer " + CultureInfo.CurrentCulture));
        stringLocalizer
            .Setup(s => s["Model_Prompt"])
            .Returns(() => new LocalizedString("Model_Prompt", "prompt from localizer " + CultureInfo.CurrentCulture));

        var stringLocalizerFactoryMock = new Mock<IStringLocalizerFactory>(MockBehavior.Strict);
        stringLocalizerFactoryMock
            .Setup(f => f.Create(It.IsAny<Type>()))
            .Returns(stringLocalizer.Object);
        var localizationOptions = new MvcDataAnnotationsLocalizationOptions();
        localizationOptions.DataAnnotationLocalizerProvider = (type, stringLocalizerFactory) =>
        {
            return stringLocalizerFactory.Create(type);
        };

        var provider = CreateProvider(options: null, localizationOptions, stringLocalizerFactoryMock.Object);

        var display = new DisplayAttribute()
        {
            Name = "Model_Name",
            Description = "Model_Description",
            Prompt = "Model_Prompt"
        };

        var attributes = new Attribute[] { display };
        var key = ModelMetadataIdentity.ForType(typeof(DataAnnotationsMetadataProviderTest));
        var context = new DisplayMetadataProviderContext(key, GetModelAttributes(attributes));

        // Act
        provider.CreateDisplayMetadata(context);

        // Assert
        using (new CultureReplacer("en-US", "en-US"))
        {
            Assert.Equal("name from localizer en-US", context.DisplayMetadata.DisplayName());
            Assert.Equal("description from localizer en-US", context.DisplayMetadata.Description());
            Assert.Equal("prompt from localizer en-US", context.DisplayMetadata.Placeholder());
        }
        using (new CultureReplacer("fr-FR", "fr-FR"))
        {
            Assert.Equal("name from localizer fr-FR", context.DisplayMetadata.DisplayName());
            Assert.Equal("description from localizer fr-FR", context.DisplayMetadata.Description());
            Assert.Equal("prompt from localizer fr-FR", context.DisplayMetadata.Placeholder());
        }
    }

    [Theory]
    [InlineData(typeof(EmptyClass), false)]
    [InlineData(typeof(ClassWithFields), false)]
    [InlineData(typeof(ClassWithProperties), false)]
    [InlineData(typeof(EmptyEnum), true)]
    [InlineData(typeof(EmptyEnum?), true)]
    [InlineData(typeof(EnumWithDisplayNames), true)]
    [InlineData(typeof(EnumWithDisplayNames?), true)]
    [InlineData(typeof(EnumWithDuplicates), true)]
    [InlineData(typeof(EnumWithDuplicates?), true)]
    [InlineData(typeof(EnumWithFlags), true)]
    [InlineData(typeof(EnumWithFlags?), true)]
    [InlineData(typeof(EnumWithFields), true)]
    [InlineData(typeof(EnumWithFields?), true)]
    [InlineData(typeof(EmptyStruct), false)]
    [InlineData(typeof(StructWithFields), false)]
    [InlineData(typeof(StructWithFields?), false)]
    [InlineData(typeof(StructWithProperties), false)]
    public void CreateDisplayMetadata_IsEnum_ReflectsModelType(Type type, bool expectedIsEnum)
    {
        // Arrange
        var provider = CreateProvider();

        var key = ModelMetadataIdentity.ForType(type);
        var attributes = new object[0];
        var context = new DisplayMetadataProviderContext(key, GetModelAttributes(attributes));

        // Act
        provider.CreateDisplayMetadata(context);

        // Assert
        Assert.Equal(expectedIsEnum, context.DisplayMetadata.IsEnum);
    }

    [Theory]
    [InlineData(typeof(EmptyClass), false)]
    [InlineData(typeof(ClassWithFields), false)]
    [InlineData(typeof(ClassWithProperties), false)]
    [InlineData(typeof(EmptyEnum), false)]
    [InlineData(typeof(EmptyEnum?), false)]
    [InlineData(typeof(EnumWithDisplayNames), false)]
    [InlineData(typeof(EnumWithDisplayNames?), false)]
    [InlineData(typeof(EnumWithDuplicates), false)]
    [InlineData(typeof(EnumWithDuplicates?), false)]
    [InlineData(typeof(EnumWithFlags), true)]
    [InlineData(typeof(EnumWithFlags?), true)]
    [InlineData(typeof(EnumWithFields), false)]
    [InlineData(typeof(EnumWithFields?), false)]
    [InlineData(typeof(EmptyStruct), false)]
    [InlineData(typeof(StructWithFields), false)]
    [InlineData(typeof(StructWithFields?), false)]
    [InlineData(typeof(StructWithProperties), false)]
    public void CreateDisplayMetadata_IsFlagsEnum_ReflectsModelType(Type type, bool expectedIsFlagsEnum)
    {
        // Arrange
        var provider = CreateProvider();

        var key = ModelMetadataIdentity.ForType(type);
        var attributes = new object[0];
        var context = new DisplayMetadataProviderContext(key, GetModelAttributes(attributes));

        // Act
        provider.CreateDisplayMetadata(context);

        // Assert
        Assert.Equal(expectedIsFlagsEnum, context.DisplayMetadata.IsFlagsEnum);
    }

    // Type -> expected EnumNamesAndValues
    public static TheoryData<Type, IReadOnlyDictionary<string, string>> EnumNamesData
    {
        get
        {
            return new TheoryData<Type, IReadOnlyDictionary<string, string>>
                {
                    { typeof(ClassWithFields), null },
                    { typeof(StructWithFields), null },
                    { typeof(StructWithFields?), null },
                    { typeof(EmptyEnum), new Dictionary<string, string>() },
                    { typeof(EmptyEnum?), new Dictionary<string, string>() },
                    {
                        typeof(EnumWithDisplayNames),
                        new Dictionary<string, string>
                        {
                            { nameof(EnumWithDisplayNames.MinusTwo), "-2" },
                            { nameof(EnumWithDisplayNames.MinusOne), "-1" },
                            { nameof(EnumWithDisplayNames.Zero), "0" },
                            { nameof(EnumWithDisplayNames.One), "1" },
                            { nameof(EnumWithDisplayNames.Two), "2" },
                            { nameof(EnumWithDisplayNames.Three), "3" },
                        }
                    },
                    {
                        typeof(EnumWithDisplayNames?),
                        new Dictionary<string, string>
                        {
                            { nameof(EnumWithDisplayNames.MinusTwo), "-2" },
                            { nameof(EnumWithDisplayNames.MinusOne), "-1" },
                            { nameof(EnumWithDisplayNames.Zero), "0" },
                            { nameof(EnumWithDisplayNames.One), "1" },
                            { nameof(EnumWithDisplayNames.Two), "2" },
                            { nameof(EnumWithDisplayNames.Three), "3" },
                        }
                    },
                    {
                        typeof(EnumWithDuplicates),
                        new Dictionary<string, string>
                        {
                            { nameof(EnumWithDuplicates.Zero), "0" },
                            { nameof(EnumWithDuplicates.None), "0" },
                            { nameof(EnumWithDuplicates.One), "1" },
                            { nameof(EnumWithDuplicates.Two), "2" },
                            { nameof(EnumWithDuplicates.Duece), "2" },
                            { nameof(EnumWithDuplicates.Three), "3" },
                            { nameof(EnumWithDuplicates.MoreThanTwo), "3" },
                        }
                    },
                    {
                        typeof(EnumWithDuplicates?),
                        new Dictionary<string, string>
                        {
                            { nameof(EnumWithDuplicates.Zero), "0" },
                            { nameof(EnumWithDuplicates.None), "0" },
                            { nameof(EnumWithDuplicates.One), "1" },
                            { nameof(EnumWithDuplicates.Two), "2" },
                            { nameof(EnumWithDuplicates.Duece), "2" },
                            { nameof(EnumWithDuplicates.Three), "3" },
                            { nameof(EnumWithDuplicates.MoreThanTwo), "3" },
                        }
                    },
                    {
                        typeof(EnumWithFlags),
                        new Dictionary<string, string>
                        {
                            { nameof(EnumWithFlags.All), "-1" },
                            { nameof(EnumWithFlags.Zero), "0" },
                            { nameof(EnumWithFlags.One), "1" },
                            { nameof(EnumWithFlags.Two), "2" },
                            { nameof(EnumWithFlags.Four), "4" },
                        }
                    },
                    {
                        typeof(EnumWithFlags?),
                        new Dictionary<string, string>
                        {
                            { nameof(EnumWithFlags.All), "-1" },
                            { nameof(EnumWithFlags.Zero), "0" },
                            { nameof(EnumWithFlags.One), "1" },
                            { nameof(EnumWithFlags.Two), "2" },
                            { nameof(EnumWithFlags.Four), "4" },
                        }
                    },
                    {
                        typeof(EnumWithFields),
                        new Dictionary<string, string>
                        {
                            { nameof(EnumWithFields.MinusTwo), "-2" },
                            { nameof(EnumWithFields.MinusOne), "-1" },
                            { nameof(EnumWithFields.Zero), "0" },
                            { nameof(EnumWithFields.One), "1" },
                            { nameof(EnumWithFields.Two), "2" },
                            { nameof(EnumWithFields.Three), "3" },
                        }
                    },
                    {
                        typeof(EnumWithFields?),
                        new Dictionary<string, string>
                        {
                            { nameof(EnumWithFields.MinusTwo), "-2" },
                            { nameof(EnumWithFields.MinusOne), "-1" },
                            { nameof(EnumWithFields.Zero), "0" },
                            { nameof(EnumWithFields.One), "1" },
                            { nameof(EnumWithFields.Two), "2" },
                            { nameof(EnumWithFields.Three), "3" },
                        }
                    },
                };
        }
    }

    [Theory]
    [MemberData(nameof(EnumNamesData))]
    public void CreateDisplayMetadata_EnumNamesAndValues_ReflectsModelType(
        Type type,
        IReadOnlyDictionary<string, string> expectedDictionary)
    {
        // Arrange
        var provider = CreateProvider();

        var key = ModelMetadataIdentity.ForType(type);
        var attributes = new object[0];
        var context = new DisplayMetadataProviderContext(key, GetModelAttributes(attributes));

        // Act
        provider.CreateDisplayMetadata(context);

        // Assert
        // This assertion does *not* require entry orders to match.
        Assert.Equal(expectedDictionary, context.DisplayMetadata.EnumNamesAndValues);
    }

    [Fact]
    public void CreateDisplayMetadata_DisplayName_LocalizeWithStringLocalizer()
    {
        // Arrange
        var expectedKeyValuePairs = new List<KeyValuePair<EnumGroupAndName, string>>
            {
                new KeyValuePair<EnumGroupAndName, string>(new EnumGroupAndName("Zero", string.Empty), "0"),
                new KeyValuePair<EnumGroupAndName, string>(new EnumGroupAndName(string.Empty, nameof(EnumWithDisplayNames.One)), "1"),
                new KeyValuePair<EnumGroupAndName, string>(new EnumGroupAndName(string.Empty, "dos value"), "2"),
                new KeyValuePair<EnumGroupAndName, string>(new EnumGroupAndName(string.Empty, "tres value"), "3"),
                new KeyValuePair<EnumGroupAndName, string>(new EnumGroupAndName(string.Empty, "name from resources"), "-2"),
                new KeyValuePair<EnumGroupAndName, string>(new EnumGroupAndName("Negatives", "menos uno value"), "-1"),
            };

        var type = typeof(EnumWithDisplayNames);
        var attributes = new object[0];

        var key = ModelMetadataIdentity.ForType(type);
        var context = new DisplayMetadataProviderContext(key, GetModelAttributes(attributes));

        var stringLocalizer = new Mock<IStringLocalizer>(MockBehavior.Strict);
        stringLocalizer
            .Setup(s => s[It.IsAny<string>()])
            .Returns<string>((index) => new LocalizedString(index, index + " value"));

        var stringLocalizerFactoryMock = new Mock<IStringLocalizerFactory>(MockBehavior.Strict);
        stringLocalizerFactoryMock
            .Setup(f => f.Create(It.IsAny<Type>()))
            .Returns(stringLocalizer.Object);

        var localizationOptions = new MvcDataAnnotationsLocalizationOptions();
        localizationOptions.DataAnnotationLocalizerProvider = (modelType, stringLocalizerFactory) => stringLocalizerFactory.Create(modelType);
        var provider = CreateProvider(options: null, localizationOptions, stringLocalizerFactoryMock.Object);

        // Act
        provider.CreateDisplayMetadata(context);

        // Assert
        Assert.Equal(
            expectedKeyValuePairs,
            context.DisplayMetadata.EnumGroupedDisplayNamesAndValues,
            KVPEnumGroupAndNameComparer.Instance);
    }

    // Type -> expected EnumDisplayNamesAndValues
    public static TheoryData<Type, IEnumerable<KeyValuePair<EnumGroupAndName, string>>> EnumDisplayNamesData
    {
        get
        {
            return new TheoryData<Type, IEnumerable<KeyValuePair<EnumGroupAndName, string>>>
                {
                    { typeof(ClassWithFields), null },
                    { typeof(StructWithFields), null },
                    { typeof(EmptyEnum), new List<KeyValuePair<EnumGroupAndName, string>>() },
                    { typeof(EmptyEnum?), new List<KeyValuePair<EnumGroupAndName, string>>() },
                    {
                        typeof(EnumWithDisplayNames),
                        new List<KeyValuePair<EnumGroupAndName, string>>
                        {
                            new KeyValuePair<EnumGroupAndName, string>(new EnumGroupAndName("Zero", string.Empty), "0"),
                            new KeyValuePair<EnumGroupAndName, string>(new EnumGroupAndName(string.Empty, nameof(EnumWithDisplayNames.One)), "1"),
                            new KeyValuePair<EnumGroupAndName, string>(new EnumGroupAndName(string.Empty, "dos"), "2"),
                            new KeyValuePair<EnumGroupAndName, string>(new EnumGroupAndName(string.Empty, "tres"), "3"),
                            new KeyValuePair<EnumGroupAndName, string>(new EnumGroupAndName(string.Empty, "name from resources"), "-2"),
                            new KeyValuePair<EnumGroupAndName, string>(new EnumGroupAndName("Negatives", "menos uno"), "-1"),
                        }
                    },
                    {
                        typeof(EnumWithDisplayNames?),
                        new List<KeyValuePair<EnumGroupAndName, string>>
                        {
                            new KeyValuePair<EnumGroupAndName, string>(new EnumGroupAndName("Zero", string.Empty), "0"),
                            new KeyValuePair<EnumGroupAndName, string>(new EnumGroupAndName(string.Empty, nameof(EnumWithDisplayNames.One)), "1"),
                            new KeyValuePair<EnumGroupAndName, string>(new EnumGroupAndName(string.Empty, "dos"), "2"),
                            new KeyValuePair<EnumGroupAndName, string>(new EnumGroupAndName(string.Empty, "tres"), "3"),
                            new KeyValuePair<EnumGroupAndName, string>(new EnumGroupAndName(string.Empty, "name from resources"), "-2"),
                            new KeyValuePair<EnumGroupAndName, string>(new EnumGroupAndName("Negatives", "menos uno"), "-1"),
                        }
                    },
                    {
                        // Note order duplicates appear cannot be inferred easily e.g. does not match the source.
                        // Zero is before None but Two is before Duece in the class below.
                        typeof(EnumWithDuplicates),
                        new List<KeyValuePair<EnumGroupAndName, string>>
                        {
                            new KeyValuePair<EnumGroupAndName, string>(new EnumGroupAndName(string.Empty, nameof(EnumWithDuplicates.Zero)), "0"),
                            new KeyValuePair<EnumGroupAndName, string>(new EnumGroupAndName(string.Empty, nameof(EnumWithDuplicates.None)), "0"),
                            new KeyValuePair<EnumGroupAndName, string>(new EnumGroupAndName(string.Empty, nameof(EnumWithDuplicates.One)), "1"),
                            new KeyValuePair<EnumGroupAndName, string>(new EnumGroupAndName(string.Empty, nameof(EnumWithDuplicates.Two)), "2"),
                            new KeyValuePair<EnumGroupAndName, string>(new EnumGroupAndName(string.Empty, nameof(EnumWithDuplicates.Duece)), "2"),
                            new KeyValuePair<EnumGroupAndName, string>(new EnumGroupAndName(string.Empty, nameof(EnumWithDuplicates.Three)), "3"),
                            new KeyValuePair<EnumGroupAndName, string>(new EnumGroupAndName(string.Empty, nameof(EnumWithDuplicates.MoreThanTwo)), "3"),
                        }
                    },
                    {
                        typeof(EnumWithDuplicates?),
                        new List<KeyValuePair<EnumGroupAndName, string>>
                        {
                            new KeyValuePair<EnumGroupAndName, string>(new EnumGroupAndName(string.Empty, nameof(EnumWithDuplicates.Zero)), "0"),
                            new KeyValuePair<EnumGroupAndName, string>(new EnumGroupAndName(string.Empty, nameof(EnumWithDuplicates.None)), "0"),
                            new KeyValuePair<EnumGroupAndName, string>(new EnumGroupAndName(string.Empty, nameof(EnumWithDuplicates.One)), "1"),
                            new KeyValuePair<EnumGroupAndName, string>(new EnumGroupAndName(string.Empty, nameof(EnumWithDuplicates.Two)), "2"),
                            new KeyValuePair<EnumGroupAndName, string>(new EnumGroupAndName(string.Empty, nameof(EnumWithDuplicates.Duece)), "2"),
                            new KeyValuePair<EnumGroupAndName, string>(new EnumGroupAndName(string.Empty, nameof(EnumWithDuplicates.Three)), "3"),
                            new KeyValuePair<EnumGroupAndName, string>(new EnumGroupAndName(string.Empty, nameof(EnumWithDuplicates.MoreThanTwo)), "3"),
                        }
                    },
                    {
                        typeof(EnumWithFlags),
                        new List<KeyValuePair<EnumGroupAndName, string>>
                        {
                            new KeyValuePair<EnumGroupAndName, string>(new EnumGroupAndName(string.Empty, nameof(EnumWithFlags.Zero)), "0"),
                            new KeyValuePair<EnumGroupAndName, string>(new EnumGroupAndName(string.Empty, nameof(EnumWithFlags.One)), "1"),
                            new KeyValuePair<EnumGroupAndName, string>(new EnumGroupAndName(string.Empty, nameof(EnumWithFlags.Two)), "2"),
                            new KeyValuePair<EnumGroupAndName, string>(new EnumGroupAndName(string.Empty, nameof(EnumWithFlags.Four)), "4"),
                            new KeyValuePair<EnumGroupAndName, string>(new EnumGroupAndName(string.Empty, nameof(EnumWithFlags.All)), "-1"),
                        }
                    },
                    {
                        typeof(EnumWithFlags?),
                        new List<KeyValuePair<EnumGroupAndName, string>>
                        {
                            new KeyValuePair<EnumGroupAndName, string>(new EnumGroupAndName(string.Empty, nameof(EnumWithFlags.Zero)), "0"),
                            new KeyValuePair<EnumGroupAndName, string>(new EnumGroupAndName(string.Empty, nameof(EnumWithFlags.One)), "1"),
                            new KeyValuePair<EnumGroupAndName, string>(new EnumGroupAndName(string.Empty, nameof(EnumWithFlags.Two)), "2"),
                            new KeyValuePair<EnumGroupAndName, string>(new EnumGroupAndName(string.Empty, nameof(EnumWithFlags.Four)), "4"),
                            new KeyValuePair<EnumGroupAndName, string>(new EnumGroupAndName(string.Empty, nameof(EnumWithFlags.All)), "-1"),
                        }
                    },
                    {
                        typeof(EnumWithFields),
                        new List<KeyValuePair<EnumGroupAndName, string>>
                        {
                            new KeyValuePair<EnumGroupAndName, string>(new EnumGroupAndName(string.Empty, nameof(EnumWithFields.Zero)), "0"),
                            new KeyValuePair<EnumGroupAndName, string>(new EnumGroupAndName(string.Empty, nameof(EnumWithFields.One)), "1"),
                            new KeyValuePair<EnumGroupAndName, string>(new EnumGroupAndName(string.Empty, nameof(EnumWithFields.Two)), "2"),
                            new KeyValuePair<EnumGroupAndName, string>(new EnumGroupAndName(string.Empty, nameof(EnumWithFields.Three)), "3"),
                            new KeyValuePair<EnumGroupAndName, string>(new EnumGroupAndName(string.Empty, nameof(EnumWithFields.MinusTwo)), "-2"),
                            new KeyValuePair<EnumGroupAndName, string>(new EnumGroupAndName(string.Empty, nameof(EnumWithFields.MinusOne)), "-1"),
                        }
                    },
                    {
                        typeof(EnumWithFields?),
                        new List<KeyValuePair<EnumGroupAndName, string>>
                        {
                            new KeyValuePair<EnumGroupAndName, string>(new EnumGroupAndName(string.Empty, nameof(EnumWithFields.Zero)), "0"),
                            new KeyValuePair<EnumGroupAndName, string>(new EnumGroupAndName(string.Empty, nameof(EnumWithFields.One)), "1"),
                            new KeyValuePair<EnumGroupAndName, string>(new EnumGroupAndName(string.Empty, nameof(EnumWithFields.Two)), "2"),
                            new KeyValuePair<EnumGroupAndName, string>(new EnumGroupAndName(string.Empty, nameof(EnumWithFields.Three)), "3"),
                            new KeyValuePair<EnumGroupAndName, string>(new EnumGroupAndName(string.Empty, nameof(EnumWithFields.MinusTwo)), "-2"),
                            new KeyValuePair<EnumGroupAndName, string>(new EnumGroupAndName(string.Empty, nameof(EnumWithFields.MinusOne)), "-1"),
                        }
                    },
                };
        }
    }

    [Theory]
    [MemberData(nameof(EnumDisplayNamesData))]
    public void CreateDisplayMetadata_EnumGroupedDisplayNamesAndValues_ReflectsModelType(
        Type type,
        IEnumerable<KeyValuePair<EnumGroupAndName, string>> expectedKeyValuePairs)
    {
        // Arrange
        var provider = CreateProvider();

        var key = ModelMetadataIdentity.ForType(type);
        var attributes = new object[0];
        var context = new DisplayMetadataProviderContext(key, GetModelAttributes(attributes));

        // Act
        provider.CreateDisplayMetadata(context);

        // Assert
        Assert.Equal(
            expectedKeyValuePairs,
            context.DisplayMetadata.EnumGroupedDisplayNamesAndValues,
            KVPEnumGroupAndNameComparer.Instance);
    }

    [Fact]
    public void CreateDisplayMetadata_EnumGroupedDisplayNamesAndValues_ReflectsDisplayAttributeOrder()
    {
        // Arrange
        var expectedKeyValuePairs = new List<KeyValuePair<EnumGroupAndName, string>>
            {
                new KeyValuePair<EnumGroupAndName, string>(new EnumGroupAndName(string.Empty, nameof(EnumWithDisplayOrder.Three)), "2"),
                new KeyValuePair<EnumGroupAndName, string>(new EnumGroupAndName(string.Empty, nameof(EnumWithDisplayOrder.Two)), "1"),
                new KeyValuePair<EnumGroupAndName, string>(new EnumGroupAndName(string.Empty, nameof(EnumWithDisplayOrder.One)), "0"),
                new KeyValuePair<EnumGroupAndName, string>(new EnumGroupAndName(string.Empty, nameof(EnumWithDisplayOrder.Null)), "3"),
            };

        var provider = CreateProvider();

        var key = ModelMetadataIdentity.ForType(typeof(EnumWithDisplayOrder));
        var attributes = new object[0];
        var context = new DisplayMetadataProviderContext(key, GetModelAttributes(attributes));

        // Act
        provider.CreateDisplayMetadata(context);

        // Assert
        Assert.Equal(
            expectedKeyValuePairs,
            context.DisplayMetadata.EnumGroupedDisplayNamesAndValues,
            KVPEnumGroupAndNameComparer.Instance);
    }

    [Fact]
    public void CreateDisplayMetadata_EnumGroupedDisplayNamesAndValues_NameWithNoIStringLocalizerAndNoResourceType()
    {
        // Arrange & Act
        var enumNameAndGroup = GetLocalizedEnumGroupedDisplayNamesAndValues(useStringLocalizer: false);

        // Assert
        var groupTwo = Assert.Single(enumNameAndGroup, e => e.Value.Equals("2", StringComparison.Ordinal));

        using (new CultureReplacer("en-US", "en-US"))
        {
            Assert.Equal("Loc_Two_Name", groupTwo.Key.Name);
        }

        using (new CultureReplacer("fr-FR", "fr-FR"))
        {
            Assert.Equal("Loc_Two_Name", groupTwo.Key.Name);
        }
    }

    [Fact]
    public void CreateDisplayMetadata_EnumGroupedDisplayNamesAndValues_NameWithIStringLocalizerAndNoResourceType()
    {
        // Arrange & Act
        var enumNameAndGroup = GetLocalizedEnumGroupedDisplayNamesAndValues(useStringLocalizer: true);

        // Assert
        var groupTwo = Assert.Single(enumNameAndGroup, e => e.Value.Equals("2", StringComparison.Ordinal));

        using (new CultureReplacer("en-US", "en-US"))
        {
            Assert.Equal("Loc_Two_Name en-US", groupTwo.Key.Name);
        }

        using (new CultureReplacer("fr-FR", "fr-FR"))
        {
            Assert.Equal("Loc_Two_Name fr-FR", groupTwo.Key.Name);
        }
    }

    [Fact]
    public void CreateDisplayMetadata_EnumGroupedDisplayNamesAndValues_NameWithNoIStringLocalizerAndResourceType()
    {
        // Arrange & Act
        var enumNameAndGroup = GetLocalizedEnumGroupedDisplayNamesAndValues(useStringLocalizer: false);

        // Assert
        var groupThree = Assert.Single(enumNameAndGroup, e => e.Value.Equals("3", StringComparison.Ordinal));

        using (new CultureReplacer("en-US", "en-US"))
        {
            Assert.Equal("type three name en-US", groupThree.Key.Name);
        }

        using (new CultureReplacer("fr-FR", "fr-FR"))
        {
            Assert.Equal("type three name fr-FR", groupThree.Key.Name);
        }
    }

    [Fact]
    public void CreateDisplayMetadata_EnumGroupedDisplayNamesAndValues_NameWithIStringLocalizerAndResourceType()
    {
        // Arrange & Act
        var enumNameAndGroup = GetLocalizedEnumGroupedDisplayNamesAndValues(useStringLocalizer: true);

        var groupThree = Assert.Single(enumNameAndGroup, e => e.Value.Equals("3", StringComparison.Ordinal));

        // Assert
        using (new CultureReplacer("en-US", "en-US"))
        {
            Assert.Equal("type three name en-US", groupThree.Key.Name);
        }

        using (new CultureReplacer("fr-FR", "fr-FR"))
        {
            Assert.Equal("type three name fr-FR", groupThree.Key.Name);
        }
    }

    [Fact]
    public void CreateValidationMetadata_RequiredAttribute_SetsIsRequiredToTrue()
    {
        // Arrange
        var provider = CreateProvider();

        var required = new RequiredAttribute();

        var attributes = new Attribute[] { required };
        var property = typeof(string).GetProperty(nameof(string.Length));
        var key = ModelMetadataIdentity.ForProperty(property, typeof(int), typeof(string));
        var context = new ValidationMetadataProviderContext(key, GetModelAttributes(new object[0], attributes));

        // Act
        provider.CreateValidationMetadata(context);

        // Assert
        Assert.True(context.ValidationMetadata.IsRequired);
    }

    [Theory]
    [InlineData(true)]
    [InlineData(false)]
    [InlineData(null)]
    public void CreateValidationMetadata_NoRequiredAttribute_IsRequiredLeftAlone(bool? initialValue)
    {
        // Arrange
        var provider = CreateProvider();

        var attributes = new Attribute[] { };
        var property = typeof(string).GetProperty(nameof(string.Length));
        var key = ModelMetadataIdentity.ForProperty(property, typeof(int), typeof(string));
        var context = new ValidationMetadataProviderContext(key, GetModelAttributes(new object[0], attributes));
        context.ValidationMetadata.IsRequired = initialValue;

        // Act
        provider.CreateValidationMetadata(context);

        // Assert
        Assert.Equal(initialValue, context.ValidationMetadata.IsRequired);
    }

    [Fact]
    public void CreateValidationMetadata_InfersRequiredAttribute_NoNonNullableProperty()
    {
        // Arrange
        var provider = CreateProvider();

        var attributes = ModelAttributes.GetAttributesForProperty(
            typeof(NullableReferenceTypes),
            typeof(NullableReferenceTypes).GetProperty(nameof(NullableReferenceTypes.NonNullableReferenceType)));
        var key = ModelMetadataIdentity.ForProperty(
            typeof(NullableReferenceTypes).GetProperty(nameof(NullableReferenceTypes.NonNullableReferenceType)),
            typeof(string),
            typeof(NullableReferenceTypes));
        var context = new ValidationMetadataProviderContext(key, attributes);

        // Act
        provider.CreateValidationMetadata(context);

        // Assert
        Assert.True(context.ValidationMetadata.IsRequired);
        var attribute = Assert.Single(context.ValidationMetadata.ValidatorMetadata, m => m is RequiredAttribute);
        Assert.True(((RequiredAttribute)attribute).AllowEmptyStrings); // non-Default for [Required]
    }

    [Fact]
    public void CreateValidationMetadata_InfersRequiredAttribute_NoNonNullableProperty_PrefersExistingRequiredAttribute()
    {
        // Arrange
        var provider = CreateProvider();

        var attributes = ModelAttributes.GetAttributesForProperty(
            typeof(NullableReferenceTypes),
            typeof(NullableReferenceTypes).GetProperty(nameof(NullableReferenceTypes.NonNullableReferenceTypeWithRequired)));

        var key = ModelMetadataIdentity.ForProperty(
            typeof(NullableReferenceTypes).GetProperty(nameof(NullableReferenceTypes.NonNullableReferenceTypeWithRequired)),
            typeof(string),
            typeof(NullableReferenceTypes));
        var context = new ValidationMetadataProviderContext(key, attributes);

        // Act
        provider.CreateValidationMetadata(context);

        // Assert
        Assert.True(context.ValidationMetadata.IsRequired);
        var attribute = Assert.Single(context.ValidationMetadata.ValidatorMetadata, m => m is RequiredAttribute a);
        Assert.Equal("Test", ((RequiredAttribute)attribute).ErrorMessage);
        Assert.False(((RequiredAttribute)attribute).AllowEmptyStrings); // Default for [Required]
    }

    [Fact]
    public void CreateValidationMetadata_SuppressRequiredInference_Noops()
    {
        // Arrange
        var provider = CreateProvider(options: new MvcOptions()
        {
            SuppressImplicitRequiredAttributeForNonNullableReferenceTypes = true,
        });

        var attributes = ModelAttributes.GetAttributesForProperty(
            typeof(NullableReferenceTypes),
            typeof(NullableReferenceTypes).GetProperty(nameof(NullableReferenceTypes.NonNullableReferenceType)));

        var key = ModelMetadataIdentity.ForProperty(
            typeof(NullableReferenceTypes).GetProperty(nameof(NullableReferenceTypes.NonNullableReferenceType)),
            typeof(string),
            typeof(NullableReferenceTypes));

        var context = new ValidationMetadataProviderContext(key, attributes);

        // Act
        provider.CreateValidationMetadata(context);

        // Assert
        Assert.Null(context.ValidationMetadata.IsRequired);
        Assert.DoesNotContain(context.ValidationMetadata.ValidatorMetadata, m => m is RequiredAttribute);
    }

    [Theory]
    [InlineData(nameof(DerivedTypeWithAllNonNullProperties.Property1))]
    [InlineData(nameof(DerivedTypeWithAllNonNullProperties.Property2))]
    public void CreateValidationMetadata_InfersRequiredAttributeOnDerivedType_BaseAnDerivedTypHaveAllNonNullProperties(string propertyName)
    {
        // Arrange
        var provider = CreateProvider();

        var modelType = typeof(DerivedTypeWithAllNonNullProperties);
        var property = modelType.GetProperty(propertyName);
        var key = ModelMetadataIdentity.ForProperty(property, property.PropertyType, modelType);
        var context = new ValidationMetadataProviderContext(key, ModelAttributes.GetAttributesForProperty(modelType, property));

        // Act
        provider.CreateValidationMetadata(context);

        // Assert
        Assert.True(context.ValidationMetadata.IsRequired);
        Assert.Contains(context.ValidationMetadata.ValidatorMetadata, m => m is RequiredAttribute);
    }

    [Fact]
    public void CreateValidationMetadata_InfersRequiredAttributeOnDerivedType_PropertyDeclaredOnBaseType()
    {
        // Arrange
        var provider = CreateProvider();

        var modelType = typeof(DerivedTypeWithAllNonNullProperties_WithNullableProperties);
        var property = modelType.GetProperty(nameof(DerivedTypeWithAllNonNullProperties_WithNullableProperties.Property1));
        var key = ModelMetadataIdentity.ForProperty(property, property.PropertyType, modelType);
        var context = new ValidationMetadataProviderContext(key, ModelAttributes.GetAttributesForProperty(modelType, property));

        // Act
        provider.CreateValidationMetadata(context);

        // Assert
        Assert.True(context.ValidationMetadata.IsRequired);
        Assert.Contains(context.ValidationMetadata.ValidatorMetadata, m => m is RequiredAttribute);
    }

    [Fact]
    public void CreateValidationMetadata_InfersRequiredAttributeOnDerivedType_NullablePropertyDeclaredOnDerviedType()
    {
        // Arrange
        var provider = CreateProvider();

        var modelType = typeof(DerivedTypeWithAllNonNullProperties_WithNullableProperties);
        var property = modelType.GetProperty(nameof(DerivedTypeWithAllNonNullProperties_WithNullableProperties.Property2));
        var key = ModelMetadataIdentity.ForProperty(property, property.PropertyType, modelType);
        var context = new ValidationMetadataProviderContext(key, ModelAttributes.GetAttributesForProperty(modelType, property));

        // Act
        provider.CreateValidationMetadata(context);

        // Assert
        Assert.Null(context.ValidationMetadata.IsRequired);
        Assert.DoesNotContain(context.ValidationMetadata.ValidatorMetadata, m => m is RequiredAttribute);
    }

    [Theory]
    [InlineData(nameof(DerivedTypeWithNullableProperties.Property1))]
    [InlineData(nameof(DerivedTypeWithNullableProperties.Property2))]
    public void CreateValidationMetadata_BaseAnDerivedTypHaveAllNullableProperties_DoesNotInferRequiredAttribute(string propertyName)
    {
        // Arrange
        var provider = CreateProvider();

        var modelType = typeof(DerivedTypeWithNullableProperties);
        var property = modelType.GetProperty(propertyName);
        var key = ModelMetadataIdentity.ForProperty(property, property.PropertyType, modelType);
        var context = new ValidationMetadataProviderContext(key, ModelAttributes.GetAttributesForProperty(modelType, property));

        // Act
        provider.CreateValidationMetadata(context);

        // Assert
        Assert.Null(context.ValidationMetadata.IsRequired);
        Assert.DoesNotContain(context.ValidationMetadata.ValidatorMetadata, m => m is RequiredAttribute);
    }

    [Fact]
    public void CreateValidationMetadata_InfersRequiredAttribute_BaseTypeIsNullable_PropertyIsNotNull()
    {
        // Tests the scenario listed in https://github.com/dotnet/aspnetcore/issues/14812
        // Arrange
        var provider = CreateProvider();

        var modelType = typeof(DerivedTypeWithNullableProperties_WithNonNullProperties);
        var property = modelType.GetProperty(nameof(DerivedTypeWithNullableProperties_WithNonNullProperties.Property2));
        var key = ModelMetadataIdentity.ForProperty(property, property.PropertyType, modelType);
        var context = new ValidationMetadataProviderContext(key, ModelAttributes.GetAttributesForProperty(modelType, property));

        // Act
        provider.CreateValidationMetadata(context);

        // Assert
        Assert.True(context.ValidationMetadata.IsRequired);
        Assert.Contains(context.ValidationMetadata.ValidatorMetadata, m => m is RequiredAttribute);
    }

    [Fact]
    public void CreateValidationMetadata_InfersRequiredAttribute_ShadowedPropertyIsNonNull()
    {
        // Arrange
        var provider = CreateProvider();

        var modelType = typeof(DerivedTypeWithNullableProperties_ShadowedProperty);
        var property = modelType.GetProperty(nameof(DerivedTypeWithNullableProperties_ShadowedProperty.Property1));
        var key = ModelMetadataIdentity.ForProperty(property, property.PropertyType, modelType);
        var context = new ValidationMetadataProviderContext(key, ModelAttributes.GetAttributesForProperty(modelType, property));

        // Act
        provider.CreateValidationMetadata(context);

        // Assert
        Assert.True(context.ValidationMetadata.IsRequired);
        Assert.Contains(context.ValidationMetadata.ValidatorMetadata, m => m is RequiredAttribute);
    }

    [Fact]
    public void CreateValidationMetadata_DoesNotInfersRequiredAttribute_TypeImplementingNonNullAbstractClass()
    {
        // Arrange
        var provider = CreateProvider();

        var modelType = typeof(TypeImplementIInterfaceWithNonNullProperty);
        var property = modelType.GetProperty(nameof(TypeImplementIInterfaceWithNonNullProperty.Property));
        var key = ModelMetadataIdentity.ForProperty(property, property.PropertyType, modelType);
        var context = new ValidationMetadataProviderContext(key, ModelAttributes.GetAttributesForProperty(modelType, property));

        // Act
        provider.CreateValidationMetadata(context);

        // Assert
        Assert.True(context.ValidationMetadata.IsRequired);
        Assert.Contains(context.ValidationMetadata.ValidatorMetadata, m => m is RequiredAttribute);
    }

    [Fact]
    public void CreateValidationMetadata_DoesNotInfersRequiredAttribute_TypeImplementingNonNullAbstractClass_NotNullable()
    {
        // Arrange
        var provider = CreateProvider();

        var modelType = typeof(TypeImplementIInterfaceWithNonNullProperty_AsNullable);
        var property = modelType.GetProperty(nameof(TypeImplementIInterfaceWithNonNullProperty_AsNullable.Property));
        var key = ModelMetadataIdentity.ForProperty(property, property.PropertyType, modelType);
        var context = new ValidationMetadataProviderContext(key, ModelAttributes.GetAttributesForProperty(modelType, property));

        // Act
        provider.CreateValidationMetadata(context);

        // Assert
        Assert.Null(context.ValidationMetadata.IsRequired);
        Assert.DoesNotContain(context.ValidationMetadata.ValidatorMetadata, m => m is RequiredAttribute);
    }

    [Fact]
    public void CreateValidationMetadata_DoesNotInfersRequiredAttribute_ReferenceTypeParameterWithDefaultValue()
    {
        // Arrange
        var provider = CreateProvider();

        // Arrange
        var type = typeof(NullableReferenceTypes);
        var method = type.GetMethod(nameof(NullableReferenceTypes.MethodWithDefault));
        var parameter = method.GetParameters().Where(p => p.Name == "defaultValueParameter").Single();
        var key = ModelMetadataIdentity.ForParameter(parameter);
        var context = new ValidationMetadataProviderContext(key, ModelAttributes.GetAttributesForParameter(parameter));

        // Act
        provider.CreateValidationMetadata(context);

        // Assert
        Assert.Null(context.ValidationMetadata.IsRequired);
        Assert.DoesNotContain(context.ValidationMetadata.ValidatorMetadata, m => m is RequiredAttribute);
    }

    [Fact]
    public void CreateValidationMetadata_InfersRequiredAttribute_NonNullableReferenceTypeParameter()
    {
        // Arrange
        var provider = CreateProvider();

        // Arrange
        var type = typeof(NullableReferenceTypes);
        var method = type.GetMethod(nameof(NullableReferenceTypes.MethodWithDefault));
        var parameter = method.GetParameters().Where(p => p.Name == "nonNullableParameter").Single();
        var key = ModelMetadataIdentity.ForParameter(parameter);
        var context = new ValidationMetadataProviderContext(key, ModelAttributes.GetAttributesForParameter(parameter));

        // Act
        provider.CreateValidationMetadata(context);

        // Assert
        Assert.True(context.ValidationMetadata.IsRequired);
        Assert.Contains(context.ValidationMetadata.ValidatorMetadata, m => m is RequiredAttribute);
    }

    [Fact]
    public void CreateValidationMetadata_WillAddValidationAttributes_From_ValidationProviderAttribute()
    {
        // Arrange
        var provider = CreateProvider();
        var validationProviderAttribute = new FooCompositeValidationAttribute(
            attributes: new List<ValidationAttribute>
            {
                    new RequiredAttribute(),
                    new StringLengthAttribute(5)
            });

        var attributes = new Attribute[] { new EmailAddressAttribute(), validationProviderAttribute };
        var property = typeof(string).GetProperty(nameof(string.Length));
        var key = ModelMetadataIdentity.ForProperty(property, typeof(int), typeof(string));
        var context = new ValidationMetadataProviderContext(key, GetModelAttributes(new object[0], attributes));

        // Act
        provider.CreateValidationMetadata(context);

        // Assert
        var expected = new List<object>
            {
                new EmailAddressAttribute(),
                new RequiredAttribute(),
                new StringLengthAttribute(5)
            };

        Assert.Equal(expected, actual: context.ValidationMetadata.ValidatorMetadata);
    }

    // [Required] has no effect on IsBindingRequired
    [Theory]
    [InlineData(true)]
    [InlineData(false)]
    public void CreateBindingMetadata_RequiredAttribute_IsBindingRequiredLeftAlone(bool initialValue)
    {
        // Arrange
        var provider = CreateProvider();

        var attributes = new Attribute[] { new RequiredAttribute() };
        var property = typeof(string).GetProperty(nameof(string.Length));
        var key = ModelMetadataIdentity.ForProperty(property, typeof(int), typeof(string));
        var context = new BindingMetadataProviderContext(key, GetModelAttributes(new object[0], attributes));
        context.BindingMetadata.IsBindingRequired = initialValue;

        // Act
        provider.CreateBindingMetadata(context);

        // Assert
        Assert.Equal(initialValue, context.BindingMetadata.IsBindingRequired);
    }

    [Theory]
    [InlineData(true)]
    [InlineData(false)]
    [InlineData(null)]
    public void CreateBindingDetails_NoEditableAttribute_IsReadOnlyLeftAlone(bool? initialValue)
    {
        // Arrange
        var provider = CreateProvider();

        var attributes = new Attribute[] { };
        var property = typeof(string).GetProperty(nameof(string.Length));
        var key = ModelMetadataIdentity.ForProperty(property, typeof(int), typeof(string));
        var context = new BindingMetadataProviderContext(key, GetModelAttributes(new object[0], attributes));
        context.BindingMetadata.IsReadOnly = initialValue;

        // Act
        provider.CreateBindingMetadata(context);

        // Assert
        Assert.Equal(initialValue, context.BindingMetadata.IsReadOnly);
    }

    [Fact]
    public void CreateValidationDetails_ValidatableObject_ReturnsObject()
    {
        // Arrange
        var provider = CreateProvider();

        var attribute = new TestValidationAttribute();
        var attributes = new Attribute[] { attribute };
        var property = typeof(string).GetProperty(nameof(string.Length));
        var key = ModelMetadataIdentity.ForProperty(property, typeof(int), typeof(string));
        var context = new ValidationMetadataProviderContext(key, GetModelAttributes(new object[0], attributes));

        // Act
        provider.CreateValidationMetadata(context);

        // Assert
        var validatorMetadata = Assert.Single(context.ValidationMetadata.ValidatorMetadata);
        Assert.Same(attribute, validatorMetadata);
    }

    [Fact]
    public void CreateValidationDetails_ValidatableObject_AlreadyInContext_Ignores()
    {
        // Arrange
        var provider = CreateProvider();

        var attribute = new TestValidationAttribute();
        var attributes = new Attribute[] { attribute };
        var property = typeof(string).GetProperty(nameof(string.Length));
        var key = ModelMetadataIdentity.ForProperty(property, typeof(int), typeof(string));
        var context = new ValidationMetadataProviderContext(key, GetModelAttributes(new object[0], attributes));
        context.ValidationMetadata.ValidatorMetadata.Add(attribute);

        // Act
        provider.CreateValidationMetadata(context);

        // Assert
        var validatorMetadata = Assert.Single(context.ValidationMetadata.ValidatorMetadata);
        Assert.Same(attribute, validatorMetadata);
    }

    [Fact]
    public void CreateValidationDetails_ForProperty()
    {
        // Arrange
        var provider = CreateProvider();

        var attribute = new TestValidationAttribute();
        var attributes = new Attribute[] { attribute };
        var property = typeof(string).GetProperty(nameof(string.Length));
        var key = ModelMetadataIdentity.ForProperty(property, typeof(int), typeof(string));
        var context = new ValidationMetadataProviderContext(key, GetModelAttributes(new object[0], attributes));
        context.ValidationMetadata.ValidatorMetadata.Add(attribute);

        // Act
        provider.CreateValidationMetadata(context);

        // Assert
        var validatorMetadata = Assert.Single(context.ValidationMetadata.ValidatorMetadata);
        Assert.Same(attribute, validatorMetadata);
    }

    [Fact]
    public void IsNonNullable_FindsNonNullableProperty()
    {
        // Arrange
        var type = typeof(NullableReferenceTypes);
        var property = type.GetProperty(nameof(NullableReferenceTypes.NonNullableReferenceType));
        var key = ModelMetadataIdentity.ForProperty(property, type, type);
        var context = new ValidationMetadataProviderContext(key, GetModelAttributes(property.GetCustomAttributes(inherit: true)));

        // Act
        var result = DataAnnotationsMetadataProvider.IsRequired(context);

        // Assert
        Assert.True(result);
    }

    [Fact]
    public void IsNullableReferenceType_ReturnsFalse_ForKeyValuePairWithoutNullableConstraints()
    {
        // Arrange
        var type = typeof(KeyValuePair<string, object>);
        var property = type.GetProperty(nameof(KeyValuePair<string, object>.Key));
        var key = ModelMetadataIdentity.ForProperty(property, type, type);
        var context = new ValidationMetadataProviderContext(key, GetModelAttributes(property.GetCustomAttributes(inherit: true)));

        // Act
        var result = DataAnnotationsMetadataProvider.IsRequired(context);

        // Assert
        Assert.False(result);
    }

#nullable enable
    [Fact]
    public void IsNullableReferenceType_ReturnsTrue_ForKeyValuePairWithNullableConstraints()
    {
        // Arrange
        var type = typeof(KeyValuePair<string, object>);
        var property = type.GetProperty(nameof(KeyValuePair<string, object>.Key))!;
        var key = ModelMetadataIdentity.ForProperty(property, type, type);
        var context = new ValidationMetadataProviderContext(key, GetModelAttributes(property.GetCustomAttributes(inherit: true)));

        // Act
        var result = DataAnnotationsMetadataProvider.IsRequired(context);

        // Assert
        // While we'd like for result to be 'true', we don't have a very good way of actually calculating it correctly.
        // This test is primarily here to document the behavior.
        Assert.False(result);
    }
#nullable restore

    [Fact]
    public void IsNonNullable_FindsNullableProperty()
    {
        // Arrange
        var type = typeof(NullableReferenceTypes);
        var property = type.GetProperty(nameof(NullableReferenceTypes.NullableReferenceType));
        var key = ModelMetadataIdentity.ForProperty(property, type, type);
        var context = new ValidationMetadataProviderContext(key, GetModelAttributes(property.GetCustomAttributes(inherit: true)));

        // Act
        var result = DataAnnotationsMetadataProvider.IsRequired(context);

        // Assert
        Assert.False(result);
    }

    [Fact]
    public void IsNonNullable_FindsNonNullableParameter()
    {
        // Arrange
        var type = typeof(NullableReferenceTypes);
        var method = type.GetMethod(nameof(NullableReferenceTypes.Method));
        var parameter = method.GetParameters().Where(p => p.Name == "nonNullableParameter").Single();
        var key = ModelMetadataIdentity.ForParameter(parameter);
        var context = new ValidationMetadataProviderContext(key, GetModelAttributes(parameter.GetCustomAttributes(inherit: true)));

        // Act
        var result = DataAnnotationsMetadataProvider.IsRequired(context);

        // Assert
        Assert.True(result);
    }

    [Fact]
    public void IsNonNullable_FindsNullableParameter()
    {
        // Arrange
        var type = typeof(NullableReferenceTypes);
        var method = type.GetMethod(nameof(NullableReferenceTypes.Method));
        var parameter = method.GetParameters().Where(p => p.Name == "nullableParameter").Single();
        var key = ModelMetadataIdentity.ForParameter(parameter);
        var context = new ValidationMetadataProviderContext(key, GetModelAttributes(parameter.GetCustomAttributes(inherit: true)));

        // Act
        var result = DataAnnotationsMetadataProvider.IsRequired(context);

        // Assert
        Assert.False(result);
    }

    private IEnumerable<KeyValuePair<EnumGroupAndName, string>> GetLocalizedEnumGroupedDisplayNamesAndValues(
        bool useStringLocalizer)
    {
        var provider = CreateIStringLocalizerProvider(useStringLocalizer);

        var key = ModelMetadataIdentity.ForType(typeof(EnumWithLocalizedDisplayNames));
        var attributes = new object[0];

        var context = new DisplayMetadataProviderContext(key, GetModelAttributes(attributes));
        provider.CreateDisplayMetadata(context);

        return context.DisplayMetadata.EnumGroupedDisplayNamesAndValues;
    }

    private DataAnnotationsMetadataProvider CreateProvider(
        MvcOptions options = null,
        MvcDataAnnotationsLocalizationOptions localizationOptions = null,
        IStringLocalizerFactory stringLocalizerFactory = null)
    {
        return new DataAnnotationsMetadataProvider(
            options ?? new MvcOptions(),
            Options.Create(localizationOptions ?? new MvcDataAnnotationsLocalizationOptions()),
            stringLocalizerFactory);
    }

    private DataAnnotationsMetadataProvider CreateIStringLocalizerProvider(bool useStringLocalizer)
    {
        var stringLocalizer = new Mock<IStringLocalizer>(MockBehavior.Strict);
        stringLocalizer
            .Setup(loc => loc[It.IsAny<string>()])
            .Returns<string>((k =>
            {
                return new LocalizedString(k, $"{k} {CultureInfo.CurrentCulture}");
            }));

        var stringLocalizerFactory = new Mock<IStringLocalizerFactory>(MockBehavior.Strict);
        stringLocalizerFactory
            .Setup(factory => factory.Create(typeof(EnumWithLocalizedDisplayNames)))
            .Returns(stringLocalizer.Object);

        var localizationOptions = new MvcDataAnnotationsLocalizationOptions();
        localizationOptions.DataAnnotationLocalizerProvider = (modelType, localizerFactory) => localizerFactory.Create(modelType);

        return CreateProvider(options: null, localizationOptions, useStringLocalizer ? stringLocalizerFactory.Object : null);
    }

    private ModelAttributes GetModelAttributes(IEnumerable<object> typeAttributes)
        => new ModelAttributes(typeAttributes, Array.Empty<object>(), Array.Empty<object>());

    private ModelAttributes GetModelAttributes(
        IEnumerable<object> typeAttributes,
        IEnumerable<object> propertyAttributes)
        => new ModelAttributes(typeAttributes, propertyAttributes, Array.Empty<object>());

    private class KVPEnumGroupAndNameComparer : IEqualityComparer<KeyValuePair<EnumGroupAndName, string>>
    {
        public static readonly IEqualityComparer<KeyValuePair<EnumGroupAndName, string>> Instance = new KVPEnumGroupAndNameComparer();

        private KVPEnumGroupAndNameComparer()
        {
        }

        public bool Equals(KeyValuePair<EnumGroupAndName, string> x, KeyValuePair<EnumGroupAndName, string> y)
        {
            using (new CultureReplacer(string.Empty, string.Empty))
            {
                return x.Key.Name.Equals(y.Key.Name, StringComparison.Ordinal)
                    && x.Key.Group.Equals(y.Key.Group, StringComparison.Ordinal);
            }
        }

        public int GetHashCode(KeyValuePair<EnumGroupAndName, string> obj)
        {
            using (new CultureReplacer(string.Empty, string.Empty))
            {
                return obj.Key.GetHashCode();
            }
        }
    }

    private class TestValidationAttribute : ValidationAttribute, IClientModelValidator
    {
        public void AddValidation(ClientModelValidationContext context)
        {
            throw new NotImplementedException();
        }
    }

    private class EmptyClass
    {
    }

    private class ClassWithFields
    {
        public const int Zero = 0;

        public const int One = 1;
    }

    private class ClassWithProperties
    {
        public int Id { get; set; }

        public string Name { get; set; }
    }

    private enum EnumWithLocalizedDisplayNames
    {
        [Display(Name = "Loc_Two_Name")]
        Two = 2,
        [Display(Name = nameof(TestResources.Type_Three_Name), ResourceType = typeof(TestResources))]
        Three = 3
    }

    private enum EmptyEnum
    {
    }

    private enum EnumWithDisplayNames
    {
        [Display(Name = "tres")]
        Three = 3,

        [Display(Name = "dos")]
        Two = 2,

        // Display attribute exists but does not set Name.
        [Display(ShortName = "uno")]
        One = 1,

        [Display(Name = "", GroupName = "Zero")]
        Zero = 0,

        [Display(Name = "menos uno", GroupName = "Negatives")]
        MinusOne = -1,

#if USE_REAL_RESOURCES
            [Display(Name = nameof(Test.Resources.DisplayAttribute_Name), ResourceType = typeof(Test.Resources))]
#else
        [Display(Name = nameof(TestResources.DisplayAttribute_Name), ResourceType = typeof(TestResources))]
#endif
        MinusTwo = -2,
    }

    private enum EnumWithDisplayOrder
    {
        [Display(Order = 3)]
        One,

        [Display(Order = 2)]
        Two,

        [Display(Order = 1)]
        Three,

        Null,
    }

    private enum EnumWithDuplicates
    {
        Zero = 0,
        One = 1,
        Three = 3,
        MoreThanTwo = 3,
        Two = 2,
        None = 0,
        Duece = 2,
    }

    [Flags]
    private enum EnumWithFlags
    {
        Four = 4,
        Two = 2,
        One = 1,
        Zero = 0,
        All = -1,
    }

    private enum EnumWithFields
    {
        MinusTwo = -2,
        MinusOne = -1,
        Three = 3,
        Two = 2,
        One = 1,
        Zero = 0,
    }

    private struct EmptyStruct
    {
    }

    private struct StructWithFields
    {
        public const int Zero = 0;

        public const int One = 1;
    }

    private struct StructWithProperties
    {
        public StructWithProperties(int id, string name)
        {
            Id = id;
            Name = name;
        }

        public int Id { get; private set; }

        public string Name { get; private set; }
    }

    private class FooCompositeValidationAttribute : ValidationProviderAttribute
    {
        private readonly IEnumerable<ValidationAttribute> _attributes;

        public FooCompositeValidationAttribute(IEnumerable<ValidationAttribute> attributes)
        {
            _attributes = attributes;
        }

        public override IEnumerable<ValidationAttribute> GetValidationAttributes()
        {
            return _attributes;
        }
    }

#nullable enable
    private class NullableReferenceTypes
    {
        public string NonNullableReferenceType { get; set; } = default!;

        [Required(ErrorMessage = "Test")]
        public string NonNullableReferenceTypeWithRequired { get; set; } = default!;

        public string? NullableReferenceType { get; set; } = default!;

        public void Method(string nonNullableParameter, string? nullableParameter)
        {
        }

        public void MethodWithDefault(string nonNullableParameter, string defaultValueParameter = "sample_data")
        {
        }
    }

    private class TypeWithAllNonNullProperties
    {
        public string Property1 { get; set; } = string.Empty;
    }

    private class DerivedTypeWithAllNonNullProperties : TypeWithAllNonNullProperties
    {
        public string Property2 { get; set; } = string.Empty;
    }

    private class DerivedTypeWithAllNonNullProperties_WithNullableProperties : TypeWithAllNonNullProperties
    {
        public string? Property2 { get; set; } = string.Empty;
    }

    private class TypeWithNullableProperties
    {
        public string? Property1 { get; set; }
    }

    private class DerivedTypeWithNullableProperties : TypeWithNullableProperties
    {
        public string? Property2 { get; set; }
    }

    private class DerivedTypeWithNullableProperties_WithNonNullProperties : TypeWithNullableProperties
    {
        public string Property2 { get; set; } = string.Empty;
    }

    private class DerivedTypeWithNullableProperties_ShadowedProperty : TypeWithNullableProperties
    {
        public new string Property1 { get; set; } = string.Empty;
    }

    public abstract class AbstraceTypehNonNullProperty
    {
        public abstract string Property { get; set; }
    }

    public class TypeImplementIInterfaceWithNonNullProperty : AbstraceTypehNonNullProperty
    {
        public override string Property { get; set; } = string.Empty;
    }
#nullable restore

    public class TypeImplementIInterfaceWithNonNullProperty_AsNullable : AbstraceTypehNonNullProperty
    {
        public override string Property { get; set; }
    }
}