c# - How to get reference to object A inside A's class?

Question

In my SharePoint 2010 c# / asp.net site, I have a class defined like

namespace PDF_Library.VisualWebPart1
{
    public partial class PDF_Library : Usercontrol   
    {
         public static PDF_Library current;
         protected void Page_Load(object sender, EventArgs e)
         {
              current = (PDF_Library)this; 
         }
    }
}


public static class Page_State
{
    public static Page is_display()
    {
        return PDF_Library.current.Page; // didn't work...
    }
}

It doesn't have a constructor. How can I get the reference to the current instance of this class ?

I tried something like this in the top

public static PDF_Library current;

Then in a function it had

current = (PDF_Library)this;

But that didn't work...

Answer 1

It is the fact that you used static in the function that was assinging current that this did not work. static is a method that is not tied to any instance of the class, therefor you can not use this .

Your only options are either make the method non-static or pass in a instance of the class as a parameter to the static function.

From what I can tell you are trying to create a " Singleton Pattern ". See the link to the previous MSDN article for examples on how to create a singleton class.

Answer 2

You need to understand that it does not work this way. Your question is tagged with asp.net - multi-user, multi-threaded environment where multiple instances of PDF_Library user control will be created all the time. It is absolutely uncertain which one of them will be hanging off PDF_Library.current . You need to rethink your design.

More on this: Page instance is disposed of when the request processing is finished. Normally this instance with all its controls and things such as Response , Request , Context etc will be set for garbage collection. Because you keep a reference to a UserControl instance in a static field, all these objects (including Page ) will be kept in memory until this current reference is replaced with something else.

Answer 3

This looks like it will have an instance. If the class is marked as static (which it doesn't appear to be) then you can just reference it by name "PDF_Library". Other wise, use ILSpy or reflector to look at the end result. I bet it has a constructor; just because you don't see one, doesn't mean it isn't there. Override the default ctor and set your instance there.

namespace PDF_Library.VisualWebPart1
{
    public partial class PDF_Library : Usercontrol   
    {
        public static PDF_Library Current;
        public PDF_Library() : base() {
           Current = this;
        }

    }
}

The problem you might be having with your Page_Load code is that it's being called too late in the lifecycle and that's why your reference call isn't working.