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CustomError Class

Configures a CustomError section to map an ASP.NET error code to a custom page. This class cannot be inherited.

Namespace:  System.Web.Configuration
Assembly:  System.Web (in System.Web.dll)

public sealed class CustomError : ConfigurationElement

The CustomError class provides a way to programmatically access and modify the error section of a configuration file. This type is part of a group that includes the CustomErrorCollection, CustomErrorsMode, and CustomErrorsSection.


When you define a custom error, ASP.NET assigns to it the standard error normally issued by the underlying service, such as IIS. For instance, if you define a custom error for the status code 404, ASP.NET will issue it anytime you refer to a non-existing .aspx page. The custom errors are only issued for those elements handled by ASP.NET. For instance, if you refer to a non-existing .htm page, IIS issues the standard 404 error.

This example demonstrates how to specify values declaratively for several attributes of the customErrors section, which can also be accessed as members of the CustomError class.

The following configuration file example shows how to specify values declaratively for the customErrors section.

<customErrors mode="RemoteOnly"
    <error statusCode="404" redirect="customerror404.htm"/>

The following code example demonstrates how to use the CustomError class.

// Get the Web application configuration.
Configuration configuration =

// Get the section.
CustomErrorsSection customErrors =

// Get the collection.
CustomErrorCollection customErrorsCollection =

Any public static (Shared in Visual Basic) members of this type are thread safe. Any instance members are not guaranteed to be thread safe.

Windows 7, Windows Vista, Windows XP SP2, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP Starter Edition, Windows Server 2008 R2, Windows Server 2008, Windows Server 2003, Windows Server 2000 SP4, Windows Millennium Edition, Windows 98

The .NET Framework and .NET Compact Framework do not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.

.NET Framework

Supported in: 3.5, 3.0, 2.0