HttpCacheValidateHandler Delegate

.NET Framework (current version)

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)

Syntax

public delegate void HttpCacheValidateHandler(
	HttpContext context,
	object data,
	ref HttpValidationStatus validationStatus
)

Parameters

context: Type: System.Web.HttpContext
The HttpContext object containing information about the current request.

data: Type: System.Object
User-supplied data used to validate the cached item.

validationStatus: Type: System.Web.HttpValidationStatus
An HttpValidationStatus enumeration value. Your delegate should set this value to indicate the result of the validation.

Remarks

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.

Examples

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;
   }
   else 
   {
      status = HttpValidationStatus.Valid;
   }
}

Version Information

.NET Framework
Available since 1.1