Are there Weak References in .NET?

I would like to keep a list of a certain class of objects in my application. But I still want the object to be garbage collected. Can you create weak references in .NET?

For reference:

• Garbage Collecting objects which keep track of their own instances in an internal Map
• Create a weak reference to an object

Answer From MSDN:

To establish a weak reference with an object, you create a WeakReference using the instance of the object to be tracked. You then set the Target property to that object and set the object to null. For a code example, see WeakReference in the class library.

From stackoverflow

• Yes, there's a generic weak reference class.

  MSDN > Weak Reference

• Can you create weak references in .NET?

  Yes:

  WeakReference r = new WeakReference(obj);
  

  Uses System.WeakReference.

• Yes...

  There is a pretty good example to be found here:

  http://web.archive.org/web/20080212232542/http://www.robherbst.com/blog/2006/08/21/c-weakreference-example/

  daub815 : FYI, the link above no longer works :(

  Andrew Rollings : Updated to refer to the wayback machine copy instead.

• Here is the full implementation sample of WeakReference

  ClassA objA = new ClassA();
  WeakReference wr = new WeakReference(objA);
  // do stuff 
  GC.Collect();
  ClassA objA2;
  if (wr.IsAlive)
      objA2 = wr.Target as ClassA; 
  else
      objA2 = new ClassA(); // create it directly if required
  

  WeakReference is in the System namespace hence no need to include any special assembly for it.