Using HttpContext for Per-Request Caching

Storing data within

HttpContext.Current.Items allows for data to exist for the duration

of the request and to be automatically discarded when the request is complete.

Public Function GetUserInfo(string username) As User

' Let's not go to the database each time we need the user's info

' the userKey is a unique value that identifies the user, such as the

' username

If (HttpContext.Current.Items(username) Is Nothing) Then

// Hang on to the data for this request only

HttpContext.Current.Items(username) = Provider.GetUserInfo(username);

End If

Return CType(HttpContext.Current.Items(username), User);

End Function

To see this code in action, see Users.cs class in the ASP.NET forums source code.

Comments

In some specialized cases, you want to cache some data only for the duration of the

request. A great example of this is in the ASP.NET forums (source code available at

www.asp.net).

The forums make use of personalization within each server control. A single page

may be composed of 10-12 server controls. Rather than each server control retrieving its

own set of data from the database, the code can reliably call the GetUserInfo() function

repeatedly. If the item is not found in the HttpContext.Items collection-a special dictionary

that exists for the duration of the request-it is created from the database and

added to HttpContext.Items.

This technique is very powerful because it allows your code to remain modular and

to take advantage of a caching technique to improve performance.