AsyncManualResetEvent.cs

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//-----------------------------------------------------------------------
// <copyright file="AsyncManualResetEvent.cs" company="Marimer LLC">
//     Copyright (c) Marimer LLC. All rights reserved.
//     Website: https://cslanet.com
// </copyright>
// <summary>Async/await implementation of a ManualResetEvent</summary>
//-----------------------------------------------------------------------
 
// Code from Stephen Toub @ Microsoft
// https://blogs.msdn.microsoft.com/pfxteam/2012/02/11/building-async-coordination-primitives-part-1-asyncmanualresetevent/
using System.Threading;
using System.Threading.Tasks;
 
namespace Csla.Threading
{
  public class AsyncManualResetEvent
  {
    private volatile TaskCompletionSource<bool> _tcs = new TaskCompletionSource<bool>();
 
    public Task WaitAsync() { return _tcs.Task; }
 
    public void Set() { _tcs.TrySetResult(true); }
 
    public void Reset()
    {
      while (true)
      {
        var tcs = _tcs;
        if (!tcs.Task.IsCompleted ||
            Interlocked.CompareExchange(ref _tcs, new TaskCompletionSource<bool>(), tcs) == tcs)
          return;
      }
    }
  }
}