C# MessageDialog.ShowAsync方法代码示例

 public async void Execute(object parameter)
 {
     var result = Task.FromResult(default(IUICommand));
     owner.DownloadVisible = false;
     owner.ProgressVisible = true;
     var folder = await downloader.VerifyFolderCreation();
     using (var client = new System.Net.Http.HttpClient())
     {
         // find all selected episodes.
         List<Task> results = new List<Task>();
         foreach (var episode in owner.selectedEpisodes)
         {
             var path = episode.Description;
             var writeTask = downloader.SaveUrlAsync(folder, client, path);
             results.Add(writeTask);
         }
         var allTasks = Task.WhenAll(results.ToArray());
         owner.ActiveDownload = allTasks;
         try
         {
             await allTasks;
         }
         catch (Exception)
         {
             // Umm, some download failed.
             var errMsg = new MessageDialog("One or more downloads failed");
             result = errMsg.ShowAsync().AsTask();
         }
         await result;
     }
     owner.DownloadVisible = true;
     owner.ProgressVisible = false;
     owner.selectedEpisodes.Clear();
 }

        /// <summary>
        /// Shows the message box.
        /// </summary>
        /// <param name="message">The message.</param>
        /// <param name="caption">The caption.</param>
        /// <param name="button">The button.</param>
        /// <param name="icon">The icon.</param>
        /// <returns>The message result.</returns>
        /// <exception cref="ArgumentException">The <paramref name="message"/> is <c>null</c> or whitespace.</exception>
        protected virtual async Task<MessageResult> ShowMessageBox(string message, string caption = "", MessageButton button = MessageButton.OK, MessageImage icon = MessageImage.None)
        {
            // TODO: Add translations for system

            var result = MessageBoxResult.None;
            var messageBoxButton = TranslateMessageButton(button);
            var messageDialog = new MessageDialog(message, caption);

            if (Enum<MessageButton>.Flags.IsFlagSet(button, MessageButton.OK) || 
                Enum<MessageButton>.Flags.IsFlagSet(button, MessageButton.OKCancel))
            {
                messageDialog.Commands.Add(new UICommand("OK", cmd => result = MessageBoxResult.OK));
            }

            if (Enum<MessageButton>.Flags.IsFlagSet(button, MessageButton.YesNo) ||
                Enum<MessageButton>.Flags.IsFlagSet(button, MessageButton.YesNoCancel))
            {
                messageDialog.Commands.Add(new UICommand("Yes", cmd => result = MessageBoxResult.Yes));
                messageDialog.Commands.Add(new UICommand("No", cmd => result = MessageBoxResult.No));
            }

            if (Enum<MessageButton>.Flags.IsFlagSet(button, MessageButton.OKCancel) ||
                Enum<MessageButton>.Flags.IsFlagSet(button, MessageButton.YesNoCancel))
            {
                messageDialog.Commands.Add(new UICommand("Cancel", cmd => result = MessageBoxResult.Cancel));
                messageDialog.CancelCommandIndex = (uint)messageDialog.Commands.Count - 1;
            }

            await messageDialog.ShowAsync();

            return TranslateMessageBoxResult(result);
        }

 private async Task DoExecute()
 {
     var result = Task.FromResult(default(IUICommand));
     try
     {
         PodcastEpisode.playbackControl.setSource(new Uri(owner.Description, UriKind.Absolute));
         PodcastEpisode.playbackControl.PlayPause();
     }
     catch (InvalidOperationException)
     {
         var errMsg = new MessageDialog("Error playing or pausing the media content");
         result = errMsg.ShowAsync().AsTask();
     }
     await result;
 }

        protected virtual IAsyncOperation<IUICommand> AlertAsync( Interaction interaction )
        {
            Arg.NotNull( interaction, nameof( interaction ) );
            Contract.Ensures( Contract.Result<IAsyncOperation<IUICommand>>() != null );

            var content = interaction.Content == null ? string.Empty : interaction.Content.ToString();
            var dialog = new MessageDialog( content, interaction.Title );

            dialog.DefaultCommandIndex = 0;

            if ( interaction.Commands.Count == 0 )
                dialog.Commands.Add( new UICommand( SR.OKCaption, DefaultAction.None ) );
            else
                dialog.Commands.Add( interaction.Commands[0].AsUICommand() );

            return dialog.ShowAsync();
        }

        protected virtual IAsyncOperation<IUICommand> PromptAsync( Interaction interaction )
        {
            Arg.NotNull( interaction, nameof( interaction ) );
            Contract.Ensures( Contract.Result<IAsyncOperation<IUICommand>>() != null );

            var content = interaction.Content == null ? string.Empty : interaction.Content.ToString();
            var dialog = new MessageDialog( content, interaction.Title );

            if ( interaction.DefaultCommandIndex >= 0 )
                dialog.DefaultCommandIndex = (uint) interaction.DefaultCommandIndex;

            if ( interaction.CancelCommandIndex >= 0 )
                dialog.CancelCommandIndex = (uint) interaction.CancelCommandIndex;

            dialog.Commands.AddRange( interaction.Commands.Select( c => c.AsUICommand() ) );

            return dialog.ShowAsync();
        }

        protected virtual MessageResult ShowMessageBox(string message, string caption = "", MessageButton button = MessageButton.OK, MessageImage icon = MessageImage.None)
#endif
        {
            Argument.IsNotNullOrWhitespace("message", message);

            var result = MessageBoxResult.None;
            var messageBoxButton = TranslateMessageButton(button);

#if NET
            var messageBoxImage = TranslateMessageImage(icon);

            var activeWindow = Application.Current.GetActiveWindow();
            if (activeWindow != null)
            {
                result = MessageBox.Show(activeWindow, message, caption, messageBoxButton, messageBoxImage);
            }
            else
            {
                result = MessageBox.Show(message, caption, messageBoxButton, messageBoxImage);
            }
#elif NETFX_CORE
            // TODO: Add translations for system

            var messageDialog = new MessageDialog(message, caption);

            if (Enum<MessageButton>.Flags.IsFlagSet(button, MessageButton.OK) || 
                Enum<MessageButton>.Flags.IsFlagSet(button, MessageButton.OKCancel))
            {
                messageDialog.Commands.Add(new UICommand("OK", cmd => result = MessageBoxResult.OK));
            }

            if (Enum<MessageButton>.Flags.IsFlagSet(button, MessageButton.YesNo) ||
                Enum<MessageButton>.Flags.IsFlagSet(button, MessageButton.YesNoCancel))
            {
                messageDialog.Commands.Add(new UICommand("Yes", cmd => result = MessageBoxResult.Yes));
                messageDialog.Commands.Add(new UICommand("No", cmd => result = MessageBoxResult.No));
            }

            if (Enum<MessageButton>.Flags.IsFlagSet(button, MessageButton.OKCancel) ||
                Enum<MessageButton>.Flags.IsFlagSet(button, MessageButton.YesNoCancel))
            {
                messageDialog.Commands.Add(new UICommand("Cancel", cmd => result = MessageBoxResult.Cancel));
                messageDialog.CancelCommandIndex = (uint)messageDialog.Commands.Count - 1;
            }

            await messageDialog.ShowAsync();
#else
            result = MessageBox.Show(message, caption, messageBoxButton);
#endif

            return TranslateMessageBoxResult(result);
        }