gistfile1.cs

public static Task<BrokeredMessage> OnMessageAsyncWrapper(CancellationToken cancellationToken = default(CancellationToken))
{
    var tcs = new TaskCompletionSource<BrokeredMessage>();
    try
    {
        if (cancellationToken.IsCancellationRequested)
        {
            tcs.SetCanceled();
            return tcs.Task;
        }

        OnMessageAsync(msg =>
                       {
                           tcs.TrySetResult(msg);
                           return tcs.Task;
                       });
    }
    catch (Exception ex)
    {
        tcs.TrySetException(ex);
    }

    return tcs.Task;
}


public static void OnMessageAsync(Func<BrokeredMessage, Task> callback)
{
    callback(default(BrokeredMessage));
}