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Handle Server-Side Errors in the Document Viewer

  • 3 min 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.

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.

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.";
        }
    }
}

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.

using System;
using DevExpress.XtraReports.Web.ClientControls;
#if NETFRAMEWORK
using System.ServiceModel;
# endif
using DevExpress.XtraReports.Web.WebDocumentViewer;

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

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.

using DevExpress.XtraReports.Web.WebDocumentViewer;

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

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.

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.";
    }
}

Register Exception Handler

To register the implemented exception handler, use the ServiceCollectionServiceExtensions class in the Startup.ConfigureServices method.

using Microsoft.Extensions.DependencyInjection;
using DevExpress.XtraReports.Web.WebDocumentViewer;
// ...

public void ConfigureServices(IServiceCollection services) {
    // ...
    services.AddSingleton<IWebDocumentViewerExceptionHandler, CustomWebDocumentViewerExceptionHandler>();
}
See Also