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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;

Windows 7, Windows Vista, Windows XP SP2, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP Starter Edition, Windows Server 2008 R2, Windows Server 2008, Windows Server 2003, Windows Server 2000 SP4, Windows Millennium Edition, Windows 98

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

.NET Framework

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