I had a debate (friendly one of course...) with a co-worker of mine, called Maayan. We discussed about what is the best place to save quite large of data that need to be used frequently in my web application, should we store it in the Application object or the prefered way - store it in the Cache object?

Before we'll go to the conclution, lets get some details about these 2 terms and the vast term called Caching in applications.

2nd before - I am not going to invent the wheel on this post, just to sharpen some points that I think that are missing or came up for most of us...

Caching is the most effective technique you can use to improve the performance of your ASP.NET web application. Designing your application with caching in mind, improves both the performance and the scalability of that application. Caching is about storing data in memory the first time it is requested and then re-using it for the following requests for a specified period of time.

ASP.NET provides very convenient API in order to use this term for the best and easy way, reffered also to Application data object and Output Cache of course.

You can cache the application data using the System.Web.Caching.Cache class. One instance of this class is created per application domain, and it remains valid as long as the application domain remains active. This object is global which means its data is avaiable anywhere at the application scope.

Now, to the big question: What is more recomended for storing the data, Cache object or Application object?

Well, the main difference between them is that he cache object has some more powerful features that allows you to control the cached data. Which this object, each of the data item has its priority state and expiration time. This object has 2 important issues handling: When your system's memory becomes short, the chache object knows to remove data items with low priorety and free its memory, by that the cahce ensures that unnecessary items does not consume valuable server resources.

One more good adventage (in ASP.NET of course) is to cache the pages' data. ASP.NET allows you to cache web pages or portions of them, calling this an output caching. By caching frequently requested pages or portions of them, you can substantially increases your web server throughput and get a fast page response. You can cache pages on devices like: the web browser making the request, the web server responding to the request, and any other cache capable devices such as proxy servers. To read some more information about it go here).

Conclution: I think that for more complex data manipulation caching, the recommended way is to use the cache object and API, but if you want to use and cache some 'dummy' data (or just data that not has to be modified and managed during the application), use the application object (or session object - per user's session) to chach your data.