I am adding caching to an ASP.NET web application. This is .NET 4, so I can use the classes in the System.Runtime.Caching namespace (which, as I understand it, was added to provide similar functionality to that found in System.Web.Caching, but for non-Web-apps.)
But since this is a web app, am I better off using System.Web.Caching? Or is the newer System.Runtime.Caching superior in some way?
Microsoft recommends using System.Runtime.Caching for all caching purposes. See this: http://msdn.microsoft.com/en-us/library/dd997357.aspx
Although, I have come across a couple threads where people are having issues with the MemoryCache.Default instance. After a while, it stops working properly. Any item you add using the Add or Set method does not actually get added to the cache. I tried the same and was able to reproduce this issue with explicitly calling MemoryCache.Default.Dispose() method.
Here are the links: MemoryCache Empty : Returns null after being set
http://forums.asp.net/t/1736572.aspx/1
My recommendation is to use the System.Web.Caching (HttpContext.Current.Cache)
UPDATE:
This issue has been fixed by MS. Check the accepted answer in the post below: Runtime Cache Issue Resolved
System.Runtime.Caching allows you to cache across all .Net apps, not just the IIS worker process. So if you have a requirement that will access the cache in multiple scenarios, use System.Runtime. Also you can check this cache adapter which allows you to swap between runtime, web, and app fabric caching. https://bitbucket.org/glav/cacheadapter
One more thing, if you have a multi-server farm, with a load balanced configuration make sure you have sticky-sessions or a distributed cache model.