Async Await Task

https://msdn.microsoft.com/en-us/library/hh873177(v=vs.110).aspx

Workload: Compute-bound Tasks or I/O-bound Tasks or Mixed

• if a method is purely compute-bound, it should be exposed only as a synchronous implementation. Let the user choice if he want to wrap it to another Task.Run (or TaskFactory.StartNew for more fine grained-control).

• All method invole I/O should have an async implementation. the TAP (Task Async Pattern) is implemented

  • with help of the compiler: async await
  • or manually with TaskCompletionSource

    • Perform the asynchronous operation, and when it completes, call the SetResult, SetException, or SetCanceled method, or the Try version of one of these methods

    • Example:

      public static Task<int> ReadTask(this Stream stream, byte[] buffer, int offset, int count, object state)
      {
        var tcs = new TaskCompletionSource<int>();
        stream.BeginRead(buffer, offset, count, ar =>
        {
            try { tcs.SetResult(stream.EndRead(ar)); }
            catch (Exception exc) { tcs.SetException(exc); }
        }, state);
        return tcs.Task;
      }