Question

If I have a .NET 4.5 asynchronous task method, for example:

 public async Task<String> GetData()

 (...)

 return await MyObject.GetSomethingAsynchronous();

And then somewhere else in a synchronous thread (e.g. a non-async method), I call this:

 String myString = MyObject.GetData().Result;

Is this safe to do or bad practice?

Answer 1

Calling Task.Result is generally not recommended. A better solution is to await the Task and change the containing method to be async, allowing the asynchronous code to grow up through the code base.

There are two problems with Task.Result as compared to await (other than the fact that it blocks rather than asynchronously waiting):

1. You can easily get into a deadlock situation where the Task needs a particular thread (e.g., a UI thread) to complete but that thread is blocked on that Task. I explain this in more detail on my blog.
2. Any errors thrown from the async method will be wrapped in an AggregateException, which makes exception handling much more complex. await will unwrap the underlying error, allowing you to use a much more natural catch(MyExceptionType).