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TPL: Composing tasks
What happens when you want to compose two distinct async operations into a single Task?
For example, let us imagine that we want to have a method that looks like this:
public void ConnectToServer() { var connection = ServerConnection.CreateServerConnection(); // tcp connect connection.HandShakeWithServer(); // application level handshake }
Now, we want to make this method async, using TPL. We can do this by changing the methods to return Task, so the API we have now is:
Task<ServerConnection> CreateServerConnectionAsync(); Task HandShakeWithServerAsync(); // instance method on ServerConnection
And we can now write the code like this:
public Task ConnectToServerAsync() { return ServerConnection.CreateServerConnectionAsymc() .ContinueWith(task => task.Result.HandShakeWithServerAsync()); }
There is just one problem with this approach, the task that we are returning is the first task, because the second task cannot be called as a chained ContinueWith.
We are actually returning a Task<Task>, so we can use task.Result.Result to wait for the final operation, but that seems like a very awkward API.
The challenge is figuring a way to compose those two operations in a way that expose only a single task.
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