HttpCacheValidateHandler Delegate
Assembly: System.Web (in system.web.dll)
'Declaration Public Delegate Sub HttpCacheValidateHandler ( _ context As HttpContext, _ data As Object, _ ByRef validationStatus As HttpValidationStatus _ ) 'Usage Dim instance As New HttpCacheValidateHandler(AddressOf HandlerMethod)
/** @delegate */ public delegate void HttpCacheValidateHandler ( HttpContext context, Object data, /** @ref */ HttpValidationStatus validationStatus )
JScript supports the use of delegates, but not the declaration of new ones.
Parameters
- context
The HttpContext object containing information about the current request.
- data
User-supplied data used to validate the cached item.
- validationStatus
An HttpValidationStatus enumeration value. Your delegate should set this value to indicate the result of the validation.
If a cached item is invalidated within the scope of the HttpCacheValidateHandler method, it is evicted from the cache and the request for the item is treated as a cache miss.
| Topic | Location |
|---|---|
| How to: Check the Validity of a Cached Page | Building ASP .NET Web Applications |
| How to: Check the Validity of a Cached Page | Building ASP .NET Web Applications |
The following code example demonstrates how to add a new cache validation delegate to an application.
Private Sub Page_Load(sender As Object, e As EventArgs) Response.Cache.AddValidationCallback(New HttpCacheValidateHandler(AddressOf CacheValidate1), Nothing) End Sub Public Sub CacheValidate1(context As HttpContext, data As Object, ByRef status As HttpValidationStatus) If context.Request.QueryString("Valid") = "false" Then status = HttpValidationStatus.Invalid Else status = HttpValidationStatus.Valid End If End Sub
private void Page_Load(Object sender, EventArgs e)
{
get_Response().get_Cache().AddValidationCallback(
new HttpCacheValidateHandler(CacheValidate1), null);
} //Page_Load
public void CacheValidate1(HttpContext context, Object data,
/**@ref*/HttpValidationStatus status)
{
if (context.get_Request().get_QueryString().get_Item("Valid").
Equals("false")) {
status = HttpValidationStatus.Invalid;
}
else {
status = HttpValidationStatus.Valid;
}
} //CacheValidate1
} //Page1
Windows 98, Windows 2000 SP4, Windows Server 2003, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP SP2, Windows XP Starter Edition
The .NET Framework does not support all versions of every platform. For a list of the supported versions, see System Requirements.