AsyncContext.md

Overview

The AsyncContext type provides a context for executing asynchronous operations. The await keyword requires a context to return back to. For most client programs, this is a UI context; for most server programs, this is a thread pool context. In most cases, you don't have to worry about it.

However, Console applications and Win32 services use the thread pool context, and AsyncContext or AsyncContextThread could be useful in those situations.

AsyncContextThread is a separate thread or task that runs an AsyncContext. AsyncContextThread does not derive from the Thread class. The thread begins running its AsyncContext immediately after creation.

AsyncContextThread will stay in its loop until it is requested to exit by another thread calling JoinAsync. Disposing an AsyncContextThread will also request it to exit, but will not wait for it to do so.

Normally, AsyncContextThread is used by windows services, but it may be used by other applications that need an independent thread with an AsyncContext.

Console Example Using AsyncContext

When using AsyncContext, you normally just call the static Run method, as such:

class Program
{
  static async Task<int> AsyncMain()
  {
    ..
  }

  static int Main(string[] args)
  {
    return AsyncContext.Run(AsyncMain);
  }
}

The Run method will return when all asynchronous operations have been completed. Any exceptions will be unwrapped and propagated.

AsyncContextThread

Unlike AsyncContext, AsyncContextThread provides properties that can be used to schedule tasks on that thread.

The Context property returns the AsyncContext being run. The Factory property returns a TaskFactory which can be used to queue work to the thread.

Platform Support

This type is available on all platforms, but may not work due to security restrictions. This is particularly a problem on Silverlight and Windows Phone platforms.