条件に合致するものを区間ごとにまとめて返す

BufferWithPredicate.cs

using System;
using System.Linq;
using System.Collections.Generic;

using Microsoft.VisualStudio.TestTools.UnitTesting;

namespace BufferWithPredicate
{
  public static class EnumerableExtensions
  {
    public static IEnumerable<T[]> Buffer<T>(
      this IEnumerable<T> source,
      Func<T, bool> pred
      )
    {
      var buffer = new List<T>();
      foreach (var x in source)
      {
        if (pred(x))
        {
          buffer.Add(x);
        }
        else
        {
          if (buffer.Count > 0)
          {
            yield return buffer.ToArray();
            buffer.Clear();
          }
        }
      }
      if (buffer.Count > 0)
      {
        yield return buffer.ToArray();
      }
    }
  }

  [TestClass]
  public class BufferWithPredicate
  {
    [TestMethod]
    public void 条件がfalseなら空()
    {
      var source = new[] { 1 };

      var result = source.Buffer(n => false);

      Assert.AreEqual(false, result.Any());
    }

    [TestMethod]
    public void 結果の組を分けてくるんで返す()
    {
      var source = new[] { 2, 3, 1, 4, 5 };

      var result = source.Buffer(n => n > 1).ToArray();

      var first = result[0].ToArray();
      Assert.AreEqual(2, first[0]);
      Assert.AreEqual(3, first[1]);

      var second = result[1].ToArray();
      Assert.AreEqual(4, second[0]);
      Assert.AreEqual(5, second[1]);
    }
  }
}