Asp.net page lifecycle-specific global variable?

Question

Surely it must be a common problem but I can't find an easy way to do this.

Is there a way to share a global variable (say a class which is expensive to instantiate) through the life cycle of an asp.net webform, without having to pass the handle to every single component of the page?

If I just create a static variable, it will be accessible by all threads in the app domain (problem: my class is not thread safe), and it will be hard to ensure that every page works on a recent copy (I want to cache the class through every step of the life cycle of the page, but I want a new instance every time a new page is called).

The alternative is to pass a handle through each control in the page, but between the master page, the page itself, and all the user controls, it makes the code quite hairy.

I was wondering if there wasn't an elegant solution to store a class in some place which is accessible only to the thread executing this particular page (including all sub user controls)?

Any suggestion welcome! Thanks Charles

Answer 1

There is a simple answer: the Items container. It is available for the lifetime of a single request and then it is automatically destroyed. You can wrap it in a property to have what you want:

 public class Foo {

   const string SOMEKEY = "_somekey";

   public static string SingleRequestVariable
   {
      get
      {
          return (string)HttpContext.Current.Items[SOMEKEY];   
      }
      set
      {
          HttpContext.Current.Items.Add( SOMEKEY, value );
      }
   }
 }

and then

Foo.SingleRequestVariable = "bar"; // somewhere
...
string val = Foo.SingleRequestVariable; // yet somewhere else