How to: Replace Standard DXRichEdit Command with a Custom Command

• Nov 05, 2023
• 2 minutes to read

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

Create a Command Descendant

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

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

Substitute a Service

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.

MainWindow.xaml.cs

void richEditControl1_Loaded(object sender, RoutedEventArgs e) {
    ReplaceRichEditCommandFactoryService(richEditControl1);
}

void ReplaceRichEditCommandFactoryService(RichEditControl control)
{
    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)
    Dim service As IRichEditCommandFactoryService = control.GetService(Of IRichEditCommandFactoryService)()
    control.ReplaceService(Of IRichEditCommandFactoryService)(New CustomRichEditCommandFactoryService(control, service))
End Sub