Handle Server-Side Errors in the Document Viewer

Aug 18, 2023
4 minutes to read

This document describes how to handle Document Viewer server-side errors. It also explains how to display detailed error information instead of a generic “Internal Server Error” message.

Tip

Online Example : How to handle server-side errors in web reporting controls

You can create a descendant from the WebDocumentViewerExceptionHandler class and override its methods to process all or specific errors. This class implements the IWebDocumentViewerExceptionHandler interface.

Handle Unknown Exceptions

The Document Viewer displays the “Internal Server Error” message in a browser for all exceptions except FaultException and DocumentCreationException. For instance, such unknown exceptions occur when you try to open a broken report layout or a file that does not exist.

You can override the GetUnknownExceptionMessage method to return a custom text or the Exception.Message property’s value as shown in the following example.

C#
VB.NET

csharp

using System;
using System.IO;
using DevExpress.XtraReports.Web.WebDocumentViewer;

public class CustomWebDocumentViewerExceptionHandler : WebDocumentViewerExceptionHandler {
    public override string GetUnknownExceptionMessage(Exception ex) {
        if (ex is FileNotFoundException) {
#if DEBUG
            return ex.Message;
#else
            return "File is not found.";
#endif
            }
        return ex.GetType().Name + " occurred. See the log file for more details.";
        }
    }
}

Imports System
Imports System.IO
Imports DevExpress.XtraReports.Web.WebDocumentViewer

Public Class CustomWebDocumentViewerExceptionHandler
    Inherits WebDocumentViewerExceptionHandler

    Public Overrides Function GetUnknownExceptionMessage(ByVal ex As Exception) As String
        If TypeOf ex Is FileNotFoundException Then
#If DEBUG Then
            Return ex.Message
#Else
            Return "File is not found."
#End If
        End If
        Return ex.GetType.Name & " occurred. See the log file for more details."
    End Function
End Class

Handle FaultException

The Document Viewer shows the Exception.Message property’s value when FaultException occurs (for instance, when you pass an invalid URL to a report storage).

Use the GetFaultExceptionMessage method to return a custom message for these exceptions as demonstrated below.

C#
VB.NET

csharp

using System;
using System.ServiceModel;
using DevExpress.XtraReports.Web.WebDocumentViewer;

public class CustomWebDocumentViewerExceptionHandler : WebDocumentViewerExceptionHandler {
    public override string GetFaultExceptionMessage(FaultException ex) {
        return "FaultException occurred: " + faultException.Message + ".";
    }
}

Imports System
Imports System.ServiceModel
Imports DevExpress.XtraReports.Web.WebDocumentViewer;

Public Class CustomWebDocumentViewerExceptionHandler
    Inherits WebDocumentViewerExceptionHandler

    Public Overrides Function GetFaultExceptionMessage(ByVal ex As FaultException) As String
        Return "FaultException occurred: " & faultException.Message & "."
    End Function
End Class

Handle DocumentCreationException

The Document Viewer displays the Exception.Message property’s value for DocumentCreationException. This exception can occur when a report document is being generated (for instance, an error arises in the BeforePrint or AfterPrint event).

You can override the GetDocumentCreationExceptionMessage method to return a custom text as shown below.

C#
VB.NET

csharp

using DevExpress.XtraReports.Web.WebDocumentViewer;

public class CustomWebDocumentViewerExceptionHandler : WebDocumentViewerExceptionHandler {
    public override string GetDocumentCreationExceptionMessage(DocumentCreationException ex) {
        return "An exception occurred while document creation.";
    }
}

Imports DevExpress.XtraReports.Web.WebDocumentViewer

Public Class CustomWebDocumentViewerExceptionHandler
    Inherits WebDocumentViewerExceptionHandler

    Public Overrides Function GetDocumentCreationExceptionMessage(ByVal ex As DocumentCreationException) As String
        Return "An exception occurred while document creation."
    End Function
End Class

Handle All Exceptions

Use the GetExceptionMessage method to handle all server-side errors independently from their types.

The code snippet below demonstrates how to override this method and return a custom text for all exceptions.

C#
VB.NET

csharp

using System;
using System.IO;
using DevExpress.XtraReports.Web.WebDocumentViewer;

public class CustomWebDocumentViewerExceptionHandler : WebDocumentViewerExceptionHandler {
    public override string GetExceptionMessage(Exception ex) {
        return ex.GetType().Name + " occurred. See the log file for more details.";
    }
}

Imports System
Imports System.IO
Imports DevExpress.XtraReports.Web.WebDocumentViewer

Public Class CustomWebDocumentViewerExceptionHandler
    Inherits WebDocumentViewerExceptionHandler

    Public Overrides Function GetExceptionMessage(ByVal ex As Exception) As String
        Return ex.GetType.Name & " occurred. See the log file for more details."
    End Function
End Class

Register Exception Handler

To register the implemented exception handler, use the static DefaultWebDocumentViewerContainer.Register method at the application’s startup.

C#
VB.NET

csharp

void Application_Start(object sender, EventArgs e) {
    // ...
    DevExpress.XtraReports.Web.WebDocumentViewer.DefaultWebDocumentViewerContainer.
        Register<IWebDocumentViewerExceptionHandler, CustomWebDocumentViewerExceptionHandler>();
}

Private Sub Application_Start(ByVal sender As Object, ByVal e As EventArgs)
    ' ...
    DevExpress.XtraReports.Web.WebDocumentViewer.DefaultWebDocumentViewerContainer.
        Register(Of IWebDocumentViewerExceptionHandler, CustomWebDocumentViewerExceptionHandler)()
End Sub