private async void TappedCommandExecute(DefaultUser user)
        {
            this.IsBusyIndicatorVisible = true;

            var loginValue = user.Login;
            var passwordValue = user.Password;
            //await Task.Factory.StartNew(async () =>
            //{
            var deviceUid = DependencyService.Get<IDeviceIdentifier>().GetIdentifier();
            var platform = Device.OS == TargetPlatform.Android ? Quickblox.Sdk.GeneralDataModel.Models.Platform.android : Quickblox.Sdk.GeneralDataModel.Models.Platform.ios;
            var userId = await App.QbProvider.LoginWithLoginValueAsync(loginValue, passwordValue, platform, deviceUid);

            Device.BeginInvokeOnMainThread(() =>
            {
                if (userId > 0)
                {
                    this.IsBusyIndicatorVisible = false;
                    App.SetMainPage();
                }
                //else
                //{
                //    App.Current.MainPage.DisplayAlert("Error", "Try to repeat login", "Ok");
                //}

                this.IsBusyIndicatorVisible = false;
            });
            //});
        }
        private async void TappedCommandExecute(DefaultUser user)
        {
            this.IsBusy = true;

            var loginValue = user.Login;
            var passwordValue = user.Password;

            var userId = await App.QbProvider.LoginWithLoginValueAsync(loginValue, passwordValue, Quickblox.Sdk.GeneralDataModel.Models.Platform.windows_phone, new DeviceUid_Uwp().GetIdentifier());

            if (userId > 0)
            {
                this.IsBusy = false;
                App.NavigationFrame.Navigate(typeof(ChatsPage), userId);
            }
            else if (userId == 0)
            {
                new MessageDialog("Try to repeat login", "Error").ShowAsync();
            }

            this.IsBusy = false;
        }