To answer this question in a single statement, you can use
HttpContext.Current.Items for very short term storage. By Short term storage, we mean that this data is valid for a single HTTP Request. There is a lot of confusion around regarding storing data in
HttpContext.Current.Items and storing data in Session variable. In this blog post, I am going to describe what are the different scenarios where we can use
HttpContext.Current.Items and what is the exact difference with session variable.
Items collections of
HttpContext is and
IDictionary key-value collections and those are shared across a single
HttpContext.Current.Items is valid for a
single HTTPRequest. Once after processing, server information is sent back to the browser, the variables that were set in the
Items collection will be lost. Whereas for
Session variable, the information is valid for multiple requests as this is user specific. The
session variable only expires either on Session Time Out or explicitly clears the values.
Let’s have a quick look at how we can store information in
HttpContext.Current.Items["ModuleInfo"] = "Custom Module Info"
And retrieve it like:
string contextData = (string)(HttpContext.Current.Items["ModuleInfo"]);
As I said,
HttpContext.Current.Items stores data for a very limited time period, then when can we use this? Yes, this is extremely useful when we want to share content between
Because each and every client request passes through the HTTP Pipeline and HTTP Pipeline consists of HTTP Module and HTTP Handler. So If you are writing one custom HTTP Module by Implementing
IHttpModule and you want pass some information from this module to the current requested page or any other module, you can use the
HttpContext.Current.Items to store the data.
Similarly, you use
HTTPContext Items collection when you are sharing the same information across the different instance based on the user request and that request could be changed for a different request.
While using Context Items collections you need to keep one things that, Items collections holds the objects, so you need to do proper type casting while retrieving it.
To summarize, in ASP.NET,
HttpContext.Current.Items allows us to hold information for a single request. We can use it to store short term information. Storing such kind of information is extremely helpful to send information across different custom modules or to requested pages. You have to make sure that the data you are using in
HttpContext.Current.Items is only valid for that current request and data should be flushed out automatically when request is sent to a browser for any new request you have to store the data again. Whereas session variable is valid for every request unless
session timeout is not reached or we explicitly clear the session.
Hope this will help!
Filed under: ASP.NET, ASP.NET 4.0, Tips and Tricks, Visual Studio