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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 void HttpCacheValidateHandler(
	HttpContext context,
	Object data,
	ref HttpValidationStatus validationStatus


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.

How to: Check the Validity of a Cached PageBuilding ASP .NET Web Applications
How to: Check the Validity of a Cached PageBuilding ASP .NET Web Applications

The following code example demonstrates how to add a new cache validation delegate to an application.

private void Page_Load(Object sender, EventArgs e)
   Response.Cache.AddValidationCallback(new HttpCacheValidateHandler(CacheValidate1), null);

public void CacheValidate1(HttpContext context, Object data, ref HttpValidationStatus status) 
   if (context.Request.QueryString["Valid"] == "false") 
      status = HttpValidationStatus.Invalid;
      status = HttpValidationStatus.Valid;

.NET Framework

Supported in: 4, 3.5, 3.0, 2.0, 1.1, 1.0

Windows 7, Windows Vista SP1 or later, Windows XP SP3, Windows XP SP2 x64 Edition, Windows Server 2008 (Server Core not supported), Windows Server 2008 R2 (Server Core supported with SP1 or later), Windows Server 2003 SP2

The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.