What is the synchronous equivalent of a TaskCompletionSource<T>?

Question

I have a method that goes like this:

Task<MyClass> MyMethodAsync()
{
    SendBluetoothMessageAsync();
    var tcs = new TaskCompletionSource<MyClass>();
    Bluetooth.MessageRecieved += (o, e) => tcs.SetResult(e.SomeProperty);
    //this removes itself afterwards, but boilerplate removed
    return await tcs.Task;
}

For my API, though, I need to offer a synchronous alternative. Therefore, I would need an object that can wait until signalled, but can carry an object. AutoResetEvent almost meets my criteria, and this is what I've got so far:

MyClass MyMethodAsync()
{
    SendBluetoothMessage();
    var are = new AutoResetEvent();
    Bluetooth.MessageRecieved += (o, e) => are.Set(); //removes itself too
    return null; //problem: how do I get the result?
}

However, I need to get the result. I can't see of a way to do this. I thought of making an EventWaitHandle derivative, but the codebehind looked distinctly odd, so I couldn't trust it. Can anyone think of a way to do this?

Answer 1

You can simply declare a local variable, set it in the callback, then return it.