HttpCacheValidateHandler Delegate
.NET Framework 3.0
Represents a method that is called to validate a cached item before the item is served from the cache.
Namespace: System.Web
Assembly: System.Web (in system.web.dll)
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 )
Not applicable.
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
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