Awaiting a Callback method

Question

I'm calling a third-party API which has a method that looks like this:

myServiceClient.Discover(key, OnCompletionCallback);

public bool OnCompletionCallback(string response)
{
    // my code
}

My challenge is, I have to call Discover because it does some work under-the-covers that I need. At the same time, I have to wait for Discover to complete before running my custom code. To further complicate matters, I can't just put my code in the OnCompletionCallback handler because I need to call the code above from a Func delegate. In short, I want to do this:

Func<SystemTask> myFunction = async () =>
{
    await myServiceClient.Discover(key);

    // my code
}

However, I can't do this because the third-party API uses a callback approach instead of an async/await approach.

Is there some way to make the callback approach work in an async / await world?

Answer 1

If I understand you correctly you can do something like this

public Task<bool> MyAsyncFunction()
{
    var tcs = new TaskCompletionSource<bool>();

    myServiceClient.Discover("somekey", s => {
        //........
        var res = true;
        tcs.TrySetResult(res);
        return res;
    });

    return tcs.Task;
}

Now you can await MyAsyncFunction