Question

Sorry if the question is dumb.

Somewhere I read that

ASP.NET supports three types of caching:

Page output caching [Output caching]

Fragment caching [Output caching]

Data caching

and somewhere

There are two different types of caching in ASP.NET:

* Application caching
* Page output caching

How many types of cache ASP.NET supports?

Answer 1

The differences are rather well summarised here:

Exploring Caching in ASP.Net

You have listed the same types of caching several times; I’d suggest reading through the link above, and, if you are having more difficulties, come back and ask some more specific questions.

To summarise the article:

1. We can use Page Output Caching for those pages whose content is relatively static. So rather than generate a page on each user request, we can cache the page using page output caching so that it can be accessed from the cache itself. Pages can be generated once and then cached for subsequent fetches. Page output caching allows the entire content of a given page to be stored in the cache.

2. Page Fragment Caching: ASP.NET provides a mechanism for caching portions of pages, called page fragment caching. To cache a portion of a page, you must first encapsulate the portion of the page you want to cache into a user control. In the user control source file, add an OutputCache directive specifying the Duration and VaryByParam attributes. When that user control is loaded into a page at runtime, it is cached, and all subsequent pages that reference that same user control will retrieve it from the cache

3. Data Caching: Caching data can dramatically improve the performance of an application by reducing database contention and round-trips. Simply, data caching stores the required data in cache so that the web server will not send requests to the DB server every time for each and every request, which increases web site performance. I’d also add that you can also store user data in this cache provided you are aware of the limitations (the length of time the data is available for, for example) as well as data from many other kinds of data store.

It can also be argued that there are several other kinds of caching ASP.Net supports; for example, you can use State Bags or just straightforward ViewState to cache data between round trips to the client. The Application and Session objects can also be used to cache data (again, with limitations) – but this really also comes under the remit of Data Caching.

In short, there are numerous places you can squirrel away data in ASP.Net – it’s more about knowing which one to use and when!