What is Absolute and Sliding expiration?

The Absolute Expiration allows you to specify the duration of the cache, beginning from the time the cache is activated. The given example shows that the cache has a cache dependency specified, as well as an expiration time of 1 minute.

Cache.Insert("announcement", announcement, depends, _ DateTime.Now.AddMinutes(1), Nothing)

The Sliding Expiration specifies that the cache will expire if a request is not made within a specified time interval. Sliding expiration policy is beneficial whenever you have a large number of items that require to be cached, as this policy enables you to keep only the most frequently accessed items in the memory. For e.g. , the following code specifies that the Cache will have a sliding duration of 1  minute. If a request is made 59 seconds after the cache is accessed, the validity of the cache would be reset to other minute.

Cache.Insert("announcement", announcement, depends, _ DateTime.MaxValue, _ TimeSpan.FromMinutes(1))