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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: 4.6, 4.5, 4, 3.5, 3.0, 2.0, 1.1
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