title: TaskAwaiter does not implement INotifyCompletion When Using Visual Studio 2015
body: <p>I have an old ASP.NET Web Form project that I need to add an async library too. I've upgraded it to .NET Framework v4.5.1. It run and compiles perfectly with Visual Studio 2013. </p>
  
  <p>However, when I open it with Visual Studio 2015, it wont compile. Every async call has a <code>TaskAwaiter does not implement INotifyCompletion</code> error.</p>
  
  <p>For instance, the following code:</p>
  
  <pre class="lang-cs prettyprint-override"><code>public async Task AsyncDelay()
  {
      await Task.Delay(1);
  }
  </code></pre>
  
  <p>Throw the following error:</p>
  
  <blockquote>
    <p>CS4027    'TaskAwaiter' does not implement 'INotifyCompletion'</p>
  </blockquote>
  
  <p>Any help at all would be appreciated.</p>