C#: Is there any way to easily find/update all references to an object?

Question

I've been reading Rockford Lhotka's "Expert C# 2008 Business Objects", where there is such a thing as a data portal which nicely abstracts where the data comes from. When using the DataPortal.Update(this), which as you might guess persists 'this' to the database, an object is returned - the persisted 'this' with any changes the db made to it, eg. a timestamp.

Lhotka has written often and very casually, that you have to make sure to update all references to the old object to the new returned object. Makes sense, but is there an easy way to find all references to the old object and change them? Obviously the GC tracks references, is it possible to tap into that?

Cheers

Answer 1

There are profiling API's to do this but nothing for general consumption. One possible solution and one which I've used myself is to implement in a base class a tracking mechanism where each instance of the object adds a WeakReference to itself to a static collection.

I have this conditionally compiled for DEBUG builds but it probably wouldn't be a good idea to rely on this in a release build.

// simplified example
// do not use. performance would suck
abstract class MyCommonBaseClass {

    static readonly List<WeakReference> instances = new List<WeakReference>();

    protected MyCommonBaseClass() {
        lock (instances) {
            RemoveDeadOnes();
            instances.Add(new WeakReference(this));
        }
    }

}