Custom Error Text for Callback Exception

• Dec 27, 2023
• 3 minutes to read

If an unhandled exception occurs while a DevExpress web control’s callback is processed on the server, ASPxHttpHandlerModule automatically catches the exception and passes an error message to the client.

The error message can contain details about the exception or a generic error message based on the customErrors mode setting defined in Web.config.

You can use one of the following approaches to modify the error message that is sent to the client:

Call the SetCallbackErrorMessage Method

Call the static SetCallbackErrorMessage(String) method in the Application_Error or CallbackError event handler in the Global.asax file. In a handler, you can use the GetLastError() method to access the source error.

Default.aspx.cs

//Generate your own exception type
protected void ASPxGridView1_RowUpdating(object sender, DevExpress.Web.Data.ASPxDataUpdatingEventArgs e) {        
    throw new CustomExceptions.MyException("Editing is disabled. Please log in as administrator.");
}

Default.aspx.vb

' Generate your own exception type
Protected Sub ASPxGridView1_RowUpdating(ByVal sender As Object, ByVal e As DevExpress.Web.Data.ASPxDataUpdatingEventArgs)
    Throw New CustomExceptions.MyException("Editing is disabled. Please log in as administrator.")
End Sub

Global.asax.cs

//Change error text in CallbackError event handler using the SetCallbackErrorMessage method 
    void Application_Start(object sender, EventArgs e){
        DevExpress.Web.ASPxWebControl.CallbackError += Callback_Error;
    }
    protected void Callback_Error(object sender, EventArgs e) {
        var exception = HttpContext.Current.Server.GetLastError();
        //Check exception type and specify error text for your exception
        if(exception is CustomExceptions.MyException) {
            DevExpress.Web.ASPxWebControl.SetCallbackErrorMessage(exception.Message);
        }
    }

Global.asax.vb

' Change error text in CallbackError event handler using the SetCallbackErrorMessage method 
Private Sub Application_Start(ByVal sender As Object, ByVal e As EventArgs)
    DevExpress.Web.ASPxWebControl.CallbackError += AddressOf Callback_Error
End Sub

Protected Sub Callback_Error(ByVal sender As Object, ByVal e As EventArgs)
    Dim exception = HttpContext.Current.Server.GetLastError()
    ' Check exception type and specify error text for your exception
    If TypeOf exception Is CustomExceptions.MyException Then
        DevExpress.Web.ASPxWebControl.SetCallbackErrorMessage(exception.Message)
    End If
End Sub

View Example: ASP.NET Web Forms Dashboard - How to handle errors

Handle the CustomErrorText Event

The CustomErrorText event allows you to define custom error text. The event is implemented for the following controls:

• ASPxCardView.CustomErrorText
• ASPxFileManager.CustomErrorText
• ASPxGridView.CustomErrorText
• ASPxScheduler.CustomErrorText
• ASPxTreeList.CustomErrorText
• ASPxVerticalGrid.CustomErrorText

In the event handler, use the e.ErrorText property to define error text and the e.Exception property to access the source error and its error message.

Default.aspx.cs

//Generate your own exception type
protected void ASPxGridView1_RowUpdating(object sender, DevExpress.Web.Data.ASPxDataUpdatingEventArgs e) {        
    throw new CustomExceptions.MyException("Editing is disabled. Please log in as administrator.");
}

//Change error text for your exception type
protected void ASPxGridView1_CustomErrorText(object sender, DevExpress.Web.ASPxGridViewCustomErrorTextEventArgs e) {        
    if(e.Exception is CustomExceptions.MyException) {
        e.ErrorText = e.Exception.Message;
    }
}

Default.aspx.vb

' Generate your own exception type
Protected Sub ASPxGridView1_RowUpdating(ByVal sender As Object, ByVal e As DevExpress.Web.Data.ASPxDataUpdatingEventArgs)
    Throw New CustomExceptions.MyException("Editing is disabled. Please log in as administrator.")
End Sub

' Change error text for your exception type
Protected Sub ASPxGridView1_CustomErrorText(ByVal sender As Object, ByVal e As DevExpress.Web.ASPxGridViewCustomErrorTextEventArgs)
    If TypeOf e.Exception Is CustomExceptions.MyException Then
        e.ErrorText = e.Exception.Message
    End If
End Sub

View Example: ASPxGridView - How to upload files in Edit mode and see them on a cell click in Browse mode