public async Task OnButtonClick(string key)
 {
     // are we waiting for using response?
     if (_userChoice != null)
     {
         _userChoice.SetResult(key);
     }
     else
     {
         // forward to calling app
         await ButtonClick.InvokeAsync(key).ConfigureAwait(true);
     }
 }
 private void OnButtonClick(string key)
 {
     ButtonClick.InvokeAsync(key);
 }