将ValueTuple转换为IEnumerable [英] Convert ValueTuple to IEnumerable

问题描述

是否有更明智的方法来进行以下操作:

Is there a saner way to do the following:

public static class ValueTupleAdditions {
  public static IEnumerable<object> ToEnumerable<A, B>(this ValueTuple<A, B> tuple) {
    yield return tuple.Item1;
    yield return tuple.Item2;
  }
  public static IEnumerable<object> ToEnumerable<A, B, C>(this ValueTuple<A, B, C> tuple) {
    yield return tuple.Item1;
    yield return tuple.Item2;
    yield return tuple.Item3;
  }

  [etc]
}

由于人们要求一个用例，因此您可以开始使用.

Since people are asking for a use case, here you go.

using Xunit;

namespace Whatever {

  public class SomeTestClass {
    public static IEnumerable<(string, Expression<Func<string, string>>, string)> RawTestData() {
      yield return ("Hello", str => str.Substring(3), "lo");
      yield return ("World", str => str.Substring(0, 4), "worl");
    }
    public static IEnumerable<object[]> StringTestData() {
      return RawTestData().Select(vt => new object[] { vt.Item1, vt.Item2, vt.Item3 });
       // would prefer to call RawTestData().Select(vt => vt.ToArray()) here, but it doesn't exist.
    }

    [Theory, MemberData(nameof(StringTestData))]
    public void RunStringTest(string input, Expression<Func<string, string>> func, string expectedOutput) {
      var output = func.Compile()(input);
      Assert.Equal(expectedOutput, output);
    }
  }
}

推荐答案

一种方法是通过

One way to do this is via the ITuple interface.

public interface ITuple
{
    int Length { get; }
    object this[int index] { get; }
}

它仅在.NET Core 2.0，Mono 5.0和.NET Framework的下一版本中可用(未发行，遵循4.7). 它不能(也永远不会)通过ValueTuple软件包作为旧框架的附件提供.

It is only available in .NET Core 2.0, Mono 5.0 and the next version of .NET Framework (unreleased, following 4.7). It is not (and will never be) available as an add-on to older frameworks via the ValueTuple package.

此API专为C#编译器使用而设计，用于以后的模式研究.

This API is designed for usage by the C# compiler for future work on patterns.

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