How to: Implement a Custom Messaging Class

• Jun 19, 2024
• 4 minutes to read

Message boxes that contain text and several buttons are be displayed in Windows Forms XAF applications in many situations. For instance, a message box is shown when an end-user closes a Detail View with modified data or cancels changes via the ModificationsController.CancelAction Action. These message boxes are provided by the Messaging class.

This class utilizes the XtraMessageBox functionality. In certain scenarios it can be required to customize the Messaging class. In this instance you should inherit this class. This topic details a way of implementing such a descendant.

Note

You can handle the Messaging.ConfirmationDialogClosed event instead of implementing a custom Messaging class, if executing a custom code after upon the closing of a message box is required.

Change the Default Focused Button

The Messaging class exposes the Messaging.Show virtual method, which displays a message box via the XtraMessageBox.Show method. The XtraMessageBox.Show overload that takes owner, text, caption, buttons and icon parameters is used by default. This overload displays a message box with the first (“OK”) button initially focused. In this example, we will override the Messaging.Show method and use another XtraMessageBox.Show method’s overload that takes the defaultButton extra parameter. Thus, it will be possible to specify which button to focus.

Add a new CustomXtraMessageBoxMessaging class to the WinForms module project (MySolution.Module.Win). If your solution does not contain this project, add this class to the WinForms application project (MySolution.Win). This class should inherit the Messaging class. Add the default public constructor and override the ShowCore method as it is shown in the snippet below.

C#

using System.Windows.Forms;
using DevExpress.ExpressApp;
using DevExpress.XtraEditors;
using DevExpress.ExpressApp.Win.Core;
// ...
public class CustomXtraMessageBoxMessaging : Messaging {
    public CustomXtraMessageBoxMessaging(XafApplication application)
        : base(application) { }
    protected override DialogResult ShowCore(
        string message, string caption, MessageBoxButtons buttons, MessageBoxIcon icon) {
        return XtraMessageBox.Show(
           message, caption, buttons, icon, MessageBoxDefaultButton.Button2);
    }
}

VB.NET

Imports System.Windows.Forms
Imports DevExpress.ExpressApp
Imports DevExpress.XtraEditors
Imports DevExpress.ExpressApp.Win.Core
' ...
Public Class CustomXtraMessageBoxMessaging
    Inherits Messaging
    Public Sub New(ByVal application As XafApplication)
        MyBase.New(application)
    End Sub
    Protected Overrides Function ShowCore( _
    ByVal message As String, ByVal caption As String, ByVal buttons As MessageBoxButtons, _
    ByVal icon As MessageBoxIcon) As DialogResult
        Return XtraMessageBox.Show(message, caption, buttons, icon, MessageBoxDefaultButton.Button2)
    End Function
End Class

Invoke the Model Editor for the Windows forms application project and navigate to the Options node. The IModelOptionsWin.Messaging property specifies the type of messaging used in Windows Forms application. Set this property value to the fully qualified name of your custom class (e.g. “CustomMessaging.Win.CustomXtraMessageBoxMessaging”).

Run the Windows Forms application. Open any persistent object’s Detail View and make some changes. Click Close. The message box with “No” button focused will be displayed.

Use a custom Message Box instead of XtraMessageBox

You can use a fully custom message box in your Messaging implementation. In the snippet below, a use of System.Windows.Forms.MessageBox class is demonstrated.

C#

using System.Windows.Forms;
using DevExpress.ExpressApp;
using DevExpress.ExpressApp.Win.Core;
// ...
public class CustomWinFormsMessageBoxMessaging : Messaging {
    public CustomWinFormsMessageBoxMessaging(XafApplication application)
        : base(application) { }
    protected override DialogResult ShowCore(
        string message, string caption, MessageBoxButtons buttons, MessageBoxIcon icon) {
        return MessageBox.Show(message, caption, buttons, icon);
    }
}

VB.NET

Imports System.Windows.Forms
Imports DevExpress.ExpressApp
Imports DevExpress.ExpressApp.Win.Core
' ...
Public Class CustomWinFormsMessageBoxMessaging
    Inherits Messaging
    Public Sub New(ByVal application As XafApplication)
        MyBase.New(application)
    End Sub
    Protected Overrides Function ShowCore( _
    ByVal message As String, ByVal caption As String, ByVal buttons As MessageBoxButtons, _
    ByVal icon As MessageBoxIcon) As DialogResult
        Return MessageBox.Show(message, caption, buttons, icon)
    End Function
End Class

Invoke the Model Editor for the Windows forms application project. Navigate to the Options node. Set the IModelOptionsWin.Messaging property to the fully qualified name of your custom class (e.g. “CustomMessaging.Win.CustomWinFormsMessageBoxMessaging”).

Run the Windows Forms application. Open any persistent object’s Detail View and make some changes. Click Close. The following message box will be displayed.