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HttpApplication.GetVaryByCustomString Method

Provides an application-wide implementation of the VaryByCustom property.

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

public virtual string GetVaryByCustomString(
	HttpContext context,
	string custom


Type: System.Web.HttpContext

An HttpContext object that contains information about the current Web request.

Type: System.String

The custom string that specifies which cached response is used to respond to the current request.

Return Value

Type: System.String
If the value of the custom parameter is "browser", the browser's Type; otherwise, null.

You can override GetVaryByCustomString to add a new method for calculating custom vary-by values that are based on the current request. The implementation has to call the base class for custom values that it does not recognize. For more information, see How to: Cache Versions of a Page Using Custom Strings.

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, 1.1, 1.0