Async BeginInvokeOnMainThread returning a result

BeginInvokeOnMainThreadAsync.cs

// from https://forums.xamarin.com/discussion/comment/154636/#Comment_154636
public static Task<T> BeginInvokeOnMainThreadAsync<T>(Func<T> a)
{
	var tcs = new TaskCompletionSource<T>();
	Device.BeginInvokeOnMainThread(() =>
		{
			try
			{
				var result = a();
				tcs.SetResult(result);
			}
			catch (Exception ex)
			{
				tcs.SetException(ex);
			}
		});
	return tcs.Task;
}