HttpCacheValidateHandler Delegate


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)

Public Delegate Sub HttpCacheValidateHandler (
	context As HttpContext,
	data As Object,
	ByRef validationStatus As HttpValidationStatus


Type: System.Web.HttpContext

The HttpContext object containing information about the current request.

Type: System.Object

User-supplied data used to validate the cached item.

Type: System.Web.HttpValidationStatus

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.

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
      status = HttpValidationStatus.Valid
   End If
End Sub

.NET Framework
Available since 1.1
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