CallWithEscapeContinuation Usage

gistfile1.cs

using System;
using System.Linq;

class Program
{
  sealed class EscapeContinuation<T> : Exception
  {
    public T Value { get; private set; }

    public void Raise(T value)
    {
      Value = value;
      throw this;
    }
  }

  static R CallWithEscapeContinuation<R>(Func<Action<R>, R> call)
  {
    var ec = new EscapeContinuation<R>();
    try
    {
      return call(ec.Raise);
    }
    catch (EscapeContinuation<R> c)
    {
      if (c == ec)
      {
        return c.Value;
      }
      else
      {
        throw;
      }
    }
  }

  static void Main(string[] args)
  {
    var index = CallWithEscapeContinuation<int>(ec =>
    {
      Enumerable.Range(0, 100).Select(x =>
      {
        if (x == 40) ec(x);
        return x;
      }).ToList();
      return -1;
    });
    Console.WriteLine(index);
  }
}