Caching in ASP.NET is relatively easy to implement, intuitive to use, and provides good means to conserve server resources by storing data in memory. The interface to caching offers a number of options to help populate cache, retrieve information, set expirations, and choose cache dependencies. You may implement caching by using the @OutputCache directive on your page or control, and program against the HttpCachePolicy class. By default, when system memory starts to become low, the cache will automatically begin removal of items that are not used as frequently. Similar to garbage collection, this process, known as scavenging, is one way cache maintains its integrity and reduces server memory usage.

With multiple ways to add items to cache, it can be confusing to know which one way is the best. The answer relies on your scenario. For example, these 3 lines of code all add items to cache.

Cache["MyData"] = myObject;
Cache.Add("MyData", myObject, null, DateTime.MaxValue, TimeSpan.FromHours(1), Caching.CacheItemPriority.Low, OnRemoveCallback);
Cache.Insert("MyData", myObject, null, DateTime.MaxValue, TimeSpan.FromHours(1));

Each allows more functionality and control over your cache management. For instance, when using the Add method, you can set a delegate to be called when the item is removed from cache to notify your application. With insert and add, you can choose expiration time intervals, sliding expirations, and dependencies. When providing a dependency, cache will remove the item when the object on which it is dependent changes.

In an app of mine, I have made caching configurable in the web.config so administrators can choose to enable, disable, and set the duration of caching. It is pretty painless and it provides those maintaining the site with the ability to adjust the application's use of server resources as they see fit.

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