Assembly: System.Web (in system.web.dll)
public function GetVaryByCustomString ( context : HttpContext, custom : String ) : String
An HttpContext that contains information about the current Web request.
The custom string that specifies which cached response is used to respond to the current request.
Return ValueIf the value of custom is "browser", the browser's Type; otherwise, a null reference (Nothing in Visual Basic).
You can override GetVaryByCustomString to add a new method for calculating custom vary-by values 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.