What is the difference between await Task<T> and Task<T>.Result?

Question

public async Task<string> GetName(int id) {     Task<string> nameTask = Task.Factory.StartNew(() => string.Format("Name matching id {0} = Developer", id));     return nameTask.Result; } 

In above method return statement I am using the Task<T>.Result property.

public async Task<string> GetName(int id) {      Task<string> nameTask = Task.Factory.StartNew(() => string.Format("Name matching id {0} = Developer", id));      return await nameTask; } 

Here I am using await Task<T>. I wont be wrong if I think that await will release the calling thread but Task<T>.Result will block it, would it be right?

Answer 1

I wont be wrong if I think that await will release the calling thread but Task.Result will block it, would it be right?

Generally, yes. await task; will "yield" the current thread. task.Result will block the current thread. await is an asynchronous wait; Result is a blocking wait.

There's another more minor difference: if the task completes in a faulted state (i.e., with an exception), then await will (re-)raise that exception as-is, but Result will wrap the exception in an AggregateException.

As a side note, avoid Task.Factory.StartNew. It's almost never the correct method to use. If you need to execute work on a background thread, prefer Task.Run.

Both Result and StartNew are appropriate if you are doing dynamic task parallelism; otherwise, they should be avoided. Neither is appropriate if you are doing asynchronous programming.