docs/csharp/language-reference/statements/snippets/iteration-statements/ForeachStatement.cs - main - aprogrammer/dotnet-docs

docs/csharp/language-reference/statements/snippets/iteration-statements/ForeachStatement.cs

81 строка2 KB

Bill Wagner

Revert collection expression for Try.nET (#40792)

16 май 2024, 16:52

16 май 2024, 16:52975b977

namespace IterationStatements;

public static class ForeachStatement
{
    public static void Examples()
    {
        ForeachWithIEnumerable();
        ForeachWithSpan();
        RefIterationVariable();
    }

    private static void ForeachWithIEnumerable()
    {
        // <WithIEnumerable>
        List<int> fibNumbers = new() { 0, 1, 1, 2, 3, 5, 8, 13 };
        foreach (int element in fibNumbers)
        {
            Console.Write($"{element} ");
        }
        // Output:
        // 0 1 1 2 3 5 8 13
        // </WithIEnumerable>
        Console.WriteLine();
    }

    private static void ForeachWithSpan()
    {
        // <WithSpan>
        Span<int> numbers = [3, 14, 15, 92, 6];
        foreach (int number in numbers)
        {
            Console.Write($"{number} ");
        }
        // Output:
        // 3 14 15 92 6
        // </WithSpan>
        Console.WriteLine();
    }

    private static void RefIterationVariable()
    {
        // <RefIterationVariable>
        Span<int> storage = stackalloc int[10];
        int num = 0;
        foreach (ref int item in storage)
        {
            item = num++;
        }
        foreach (ref readonly var item in storage)
        {
            Console.Write($"{item} ");
        }
        // Output:
        // 0 1 2 3 4 5 6 7 8 9
        // </RefIterationVariable>
        Console.WriteLine();
    }

    private static async Task AwaitForeachExample()
    {
        // <AwaitForeach>
        await foreach (var item in GenerateSequenceAsync())
        {
            Console.WriteLine(item);
        }
        // </AwaitForeach>

    }

    private static async IAsyncEnumerable<int> GenerateSequenceAsync()
    {
        for (int i = 0; i < 40; i++)
        {
            if (i % 10 == 0)
            {
                await Task.Delay(2000);
            }
            yield return i;
        }
    }
}