How to: Replace Standard DXRichEdit Command with a Custom Command

• Jul 11, 2018
• 2 minutes to read

The following example describes how to replace the built-in command with a custom one using the service substitution technique.

1. Create a target command descendant and override its required members.

   In this example, the CustomSaveDocumentCommand class is a SaveDocumentCommand descendant. It overrides the ExecuteCore method to display a message after a document has been saved.

   View Example

   CustomRichEditCommandFactoryService.cs

   public class CustomSaveDocumentCommand:SaveDocumentCommand{
       public CustomSaveDocumentCommand(IRichEditControl control)
           : base(control)
       {
       }
       protected override void ExecuteCore()
       {
             base.ExecuteCore();
             MessageBox.Show("Custom SaveDocument command was executed");
       }
   }
   

   CustomRichEditCommandFactoryService.vb

   Public Class CustomSaveDocumentCommand
       Inherits SaveDocumentCommand
   
       Public Sub New(ByVal control As IRichEditControl)
           MyBase.New(control)
       End Sub
       Protected Overrides Sub ExecuteCore()
             MyBase.ExecuteCore()
             MessageBox.Show("Custom SaveDocument command was executed")
       End Sub
   End Class
   

2. Implement the IRichEditCommandFactoryService descendant. Create a CreateCommand method to generate a new custom command object used to replace the built-in command.

   View Example

   CustomRichEditCommandFactoryService.cs

   public class CustomRichEditCommandFactoryService : IRichEditCommandFactoryService
   {
       readonly IRichEditCommandFactoryService service;
       readonly RichEditControl control;
   
       public CustomRichEditCommandFactoryService(RichEditControl control,
           IRichEditCommandFactoryService service) {
           Guard.ArgumentNotNull(control, "control");
           Guard.ArgumentNotNull(service, "service");
           this.control = control;
           this.service = service;
       }
   
       public RichEditCommand CreateCommand(RichEditCommandId id) {
           if(id == RichEditCommandId.FileSave)
               return new CustomSaveDocumentCommand(control);
   
           return service.CreateCommand(id);
       }
   }
   

   CustomRichEditCommandFactoryService.vb

   Public Class CustomRichEditCommandFactoryService
       Implements IRichEditCommandFactoryService
   
       Private ReadOnly service As IRichEditCommandFactoryService
       Private ReadOnly control As RichEditControl
   
       Public Sub New(ByVal control As RichEditControl, ByVal service As IRichEditCommandFactoryService)
           Guard.ArgumentNotNull(control, "control")
           Guard.ArgumentNotNull(service, "service")
           Me.control = control
           Me.service = service
       End Sub
   
       Public Function CreateCommand(ByVal id As RichEditCommandId) As RichEditCommand Implements IRichEditCommandFactoryService.CreateCommand
           If id = RichEditCommandId.FileSave Then
               Return New CustomSaveDocumentCommand(control)
           End If
   
           Return service.CreateCommand(id)
       End Function
   End Class
   

3. In the RichEditControl.Loaded event handler, create a new IRichEditCommandFactoryService descendant instance and use the RichEditControl.ReplaceService<T> method to substitute the default service with the newly created service.

   View Example

   MainWindow.xaml.cs

   void richEditControl1_Loaded(object sender, RoutedEventArgs e) {
       ReplaceRichEditCommandFactoryService(richEditControl1);
   }
   
   void ReplaceRichEditCommandFactoryService(RichEditControl control)
   {
       control.ApplyTemplate();
       IRichEditCommandFactoryService service = control.GetService<IRichEditCommandFactoryService>();
       control.ReplaceService<IRichEditCommandFactoryService>(new CustomRichEditCommandFactoryService(control, service));
   }
   

   MainWindow.xaml.vb

   Private Sub richEditControl1_Loaded(ByVal sender As Object, ByVal e As RoutedEventArgs)
       ReplaceRichEditCommandFactoryService(richEditControl1)
   End Sub
   
   Private Sub ReplaceRichEditCommandFactoryService(ByVal control As RichEditControl)
       control.ApplyTemplate()
       Dim service As IRichEditCommandFactoryService = control.GetService(Of IRichEditCommandFactoryService)()
       control.ReplaceService(Of IRichEditCommandFactoryService)(New CustomRichEditCommandFactoryService(control, service))
   End Sub