docs/csharp/language-reference/operators/snippets/shared/NewOperator.cs - main - aprogrammer/dotnet-docs

docs/csharp/language-reference/operators/snippets/shared/NewOperator.cs
96 строк3 KB
Bill Wagner
Revert collection expressions (#38582)
11 дек 2023, 16:00
11 дек 2023, 16:00ed1be7d
namespace operators;

public static class NewOperator
{
    public static void Examples()
    {
        Constructor();
        ConstructorWithInitializer();
        Array();
        ArrayInitialization();
        AnonymousType();
    }

    private static void Constructor()
    {
        // <SnippetConstructor>
        var dict = new Dictionary<string, int>();
        dict["first"] = 10;
        dict["second"] = 20;
        dict["third"] = 30;

        Console.WriteLine(string.Join("; ", dict.Select(entry => $"{entry.Key}: {entry.Value}")));
        // Output:
        // first: 10; second: 20; third: 30
        // </SnippetConstructor>
    }

    private static void ConstructorWithInitializer()
    {
        // <SnippetConstructorWithInitializer>
        var dict = new Dictionary<string, int>
        {
            ["first"] = 10,
            ["second"] = 20,
            ["third"] = 30
        };

        Console.WriteLine(string.Join("; ", dict.Select(entry => $"{entry.Key}: {entry.Value}")));
        // Output:
        // first: 10; second: 20; third: 30
        // </SnippetConstructorWithInitializer>
    }

    private static void TargetTyped()
    {
        // <SnippetTargetTyped>
        List<int> xs = new();
        List<int> ys = new(capacity: 10_000);
        List<int> zs = new() { Capacity = 20_000 };

        Dictionary<int, List<int>> lookup = new()
        {
            [1] = new() { 1, 2, 3 },
            [2] = new() { 5, 8, 3 },
            [5] = new() { 1, 0, 4 }
        };
        // </SnippetTargetTyped>
    }

    private static void Array()
    {
        // This snippet is used with try.net,
        // which doesn't support collection expressions yet.
        // <SnippetArray>
        var numbers = new int[3];
        numbers[0] = 10;
        numbers[1] = 20;
        numbers[2] = 30;
        Console.WriteLine(string.Join(", ", numbers));
        // Output:
        // 10, 20, 30
        // </SnippetArray>
    }

    private static void ArrayInitialization()
    {
        // This snippet is used with try.net,
        // which doesn't support collection expressions yet.
        // <SnippetArrayInitialization>
        var a = new int[3] { 10, 20, 30 };
        var b = new int[] { 10, 20, 30 };
        var c = new[] { 10, 20, 30 };
        Console.WriteLine(c.GetType());  // output: System.Int32[]
        // </SnippetArrayInitialization>
    }

    private static void AnonymousType()
    {
        // <SnippetAnonymousType>
        var example = new { Greeting = "Hello", Name = "World" };
        Console.WriteLine($"{example.Greeting}, {example.Name}!");
        // Output:
        // Hello, World!
        // </SnippetAnonymousType>
    }
}