await without TPL

CustomAwaiter.cs

private async void AsyncMethod() {
    var result = await Method();
}

MyTask<Int32> Method() {
    return new MyTask<Int32>();
}


// ------------------------------------------------------------


public class MyTask<T> {
    public Boolean IsCompleted { get { throw new NotImplementedException(); } }
    public Boolean Result { get { throw new NotImplementedException(); } }

    public void ContinueWith(Action continuation) {
        throw new NotImplementedException();
    }
}

public static class MyTaskExtensions {
    public static MyAwaiter<T> GetAwaiter<T>(this MyTask<T> task) {
        return new MyAwaiter<T>(task);
    }
}

public class MyAwaiter<T> : INotifyCompletion {
    private readonly MyTask<T> task;

    public MyAwaiter(MyTask<T> task) {
        this.task = task;
    }

    public Boolean IsCompleted
    {
        get { return task.IsCompleted; }
    }

    public void OnCompleted(Action continuation) {
        var context = SynchronizationContext.Current;
        if (context == null) {
            task.ContinueWith(continuation);
        } else {
            // with usage of context
            task.ContinueWith(continuation);
        }
    }

    public T GetResult() {
        return task.Result;
    }
}