RAD Studio VCL Reference
TWebRequest.CacheControl Property

Reports the value of the Cache-Control header of the HTTP request message.

property CacheControl: AnsiString;
__property AnsiString CacheControl;

Read CacheControl to determine any Web client directives that must be obeyed by all caching mechanisms along the request/response chain. The CacheControl directives of the HTTP request need not apply to the corresponding HTTP response.  

The HTTP 1.1 standard defines the following directives for CacheControl:

The request may not be cached. The Web server validates the request before the TWebRequest object is created.  
The request contains sensitive information and may not be stored on any permanent medium such as a backup tape. If the request is stored temporarily in a file, the file must be deleted.  
The request is considered invalid if it is older than ss seconds. This directive takes precedence over the Expires property, even if Expires is more restrictive. Invalid requests are validated by the Web server before the TWebRequest object is created.  
max-stale or max-stale=ss  
The client is willing to accept a response that has exceeded its expiration time. The max-stale directive can optionally specify the number of seconds by which the response can exceed its expiration time.  
The client is not willing to accept a response that expires in less than ss seconds.  


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