Response Redirection on Callback Exceptions

Oct 29, 2020
4 minutes to read

When an unhandled exception occurs during server-side callback processing, the ASPxHttpHandlerModule prevents an application from becoming unresponsive by sending a specific response to the client. Specify the required page name in the Web.Config file’s Redirection on a Callback Error option to redirect the response to a page that displays error information – as shown below.

<configuration>
  ...
  <devExpress>
    ...
    <errors callbackErrorRedirectUrl="~/Error.aspx" />
  </devExpress>
</configuration>

Note that the callbackErrorRedirectUrl property value should contain the subdirectory name (if it requires) and have the following format:

/subdir/Home/Error

Note

MVC-Specific Note The callbackErrorRedirectUrl property value should contain a subdirectory name (“/{sub-directory}/Home/Error”) if a MVC application’s root URL meets the following conditions:

The URL is overridden using the IIS Web Server.
The URL contains a subdirectory (for example, “http://localhost/{sub-directory}”).

Typically, the page to which the response is redirected shows information about the server exception. Use the static ASPxWebControl.GetCallbackErrorMessage method while the page redirect is processed, to obtain exception-related information. For example, you can execute the code below on page load.

C#
VB.NET

using DevExpress.Web.ASPxClasses;

public partial class Error : Page {
    protected void Page_Load(object sender, EventArgs e) {
        string errorMessage = ASPxWebControl.GetCallbackErrorMessage();
        Response.Output.Write(errorMessage);
    }
}

Imports DevExpress.Web.ASPxClasses

Public Partial Class [Error]
    Inherits Page
    Protected Sub Page_Load(ByVal sender As Object, ByVal e As EventArgs)
        Dim errorMessage As String = ASPxWebControl.GetCallbackErrorMessage()
        Response.Output.Write(errorMessage)
    End Sub
End Class

Example

In this example, the error message is displayed within the redirected page (Error.aspx) after an exception occurs on a callback within the Default.aspx page.

The redirection page is specified within the devExpress -> errors section of the web.config file via the callbackErrorRedirectUrl key (see Redirection on a Callback Error). The error message is obtained by using the static ASPxWebControl.GetCallbackErrorMessage method.

Note

To provide the message redirection between pages, the ASPxHttpHandlerModule should be registered within the web.config file.

Note

A complete sample project is available at https://github.com/DevExpress-Examples/how-to-get-the-error-message-by-using-the-getcallbackerrormessage-static-method-e1988

<%@ Page Language="C#" AutoEventWireup="true"  CodeFile="Default.aspx.cs" Inherits="_Default" %>
<%@ Register Assembly="DevExpress.Web.ASPxEditors.v10.1" Namespace="DevExpress.Web.ASPxEditors" TagPrefix="dx" %>
<%@ Register Assembly="DevExpress.Web.v10.1" Namespace="DevExpress.Web.ASPxCallback" TagPrefix="dx" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">

<html xmlns="http://www.w3.org/1999/xhtml" >
<head runat="server">
    <title>Untitled Page</title>
</head>
<body>
    <form id="form1" runat="server">
        <dx:ASPxButton id="ASPxButton1" runat="server" AutoPostBack="False" text="Perform Callback">
            <ClientSideEvents Click="function(s, e) { callback1.PerformCallback(); }"></ClientSideEvents>
        </dx:ASPxButton>
        <dx:ASPxCallback ID="ASPxCallback1" runat="server" ClientInstanceName="callback1"></dx:ASPxCallback>
    </form>
</body>
</html>

using System;
using System.Web.UI;

public partial class _Default : Page {
    protected void Page_Load(object sender, EventArgs e) {
        if(IsCallback) {
            NotImplementedException innerException = new NotImplementedException("NoReport");
            throw new NotImplementedException("This message has been generated for a GetCallbackErrorMessage() method demonstration.", innerException);
        }
    }
}

<%@ Page Language="C#" AutoEventWireup="true" CodeFile="Error.aspx.cs" Inherits="Error" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">

<html xmlns="http://www.w3.org/1999/xhtml" >
<head runat="server">
    <title>Error</title>
</head>
<body>
    <form id="form1" runat="server">
    </form>
</body>
</html>

using System;
using System.Web.UI;
using DevExpress.Web.ASPxClasses;

public partial class Error : Page {
    protected void Page_Load(object sender, EventArgs e) {
        string errorMessage = ASPxWebControl.GetCallbackErrorMessage();
        Response.Output.Write(errorMessage);
    }
}

<%@ Page Language="vb" AutoEventWireup="true" CodeFile="Error.aspx.vb" Inherits="Error" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">

<html xmlns="http://www.w3.org/1999/xhtml" >
<head runat="server">
    <title>Error</title>
</head>
<body>
    <form id="form1" runat="server">
    </form>
</body>
</html>

Imports System
Imports System.Web.UI

Partial Public Class _Default
    Inherits Page

    Protected Sub Page_Load(ByVal sender As Object, ByVal e As EventArgs)
        If IsCallback Then
            Dim innerException As New NotImplementedException("NoReport")
            Throw New NotImplementedException("This message has been generated for a GetCallbackErrorMessage() method demonstration.", innerException)
        End If
    End Sub
End Class

<%@ Page Language="vb" AutoEventWireup="true"  CodeFile="Default.aspx.vb" Inherits="_Default" %>
<%@ Register Assembly="DevExpress.Web.ASPxEditors.v10.1" Namespace="DevExpress.Web.ASPxEditors" TagPrefix="dx" %>
<%@ Register Assembly="DevExpress.Web.v10.1" Namespace="DevExpress.Web.ASPxCallback" TagPrefix="dx" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">

<html xmlns="http://www.w3.org/1999/xhtml" >
<head runat="server">
    <title>Untitled Page</title>
</head>
<body>
    <form id="form1" runat="server">
        <dx:ASPxButton id="ASPxButton1" runat="server" AutoPostBack="False" text="Perform Callback">
            <ClientSideEvents Click="function(s, e) { callback1.PerformCallback(); }"></ClientSideEvents>
        </dx:ASPxButton>
        <dx:ASPxCallback ID="ASPxCallback1" runat="server" ClientInstanceName="callback1"></dx:ASPxCallback>
    </form>
</body>
</html>

Imports System
Imports System.Web.UI
Imports DevExpress.Web.ASPxClasses

Partial Public Class [Error]
    Inherits Page

    Protected Sub Page_Load(ByVal sender As Object, ByVal e As EventArgs)
        Dim errorMessage As String = ASPxWebControl.GetCallbackErrorMessage()
        Response.Output.Write(errorMessage)
    End Sub
End Class

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