Hi Matt,

i'v emailed infragistics support about this, and they say the same thing -> Infragistics control hook to static events.

1. The correct way to handle garbage collection in this case would have been to use weak references in the event, as in:

 http://diditwith.net/PermaLink,guid,aacdb8ae-7baa-4423-a953-c18c1c7940ab.aspx

this will allow the objects to get collected , and their dispose method to be called implicitly by the distructor.

2. Regarding SupressFinalize, GC.SupressFinalize does not prevent the call to Dispose, but rather the redundent call to Dispose by the GC after Dispose have been called once already (the point of this function call is to prevent aggressive GC to cause rentries to the Dispose method).

As for the Control call to SupressFinalize, this call is done by the call to base.Dispose by the extending child, so in any case it's called only after the child's Dispose has executed.

3. Regarding best practices, destructors are not common and not widely used, however calling Dispose is exactly the kind of good reason you need for a destructor. it's exactly why microsoft implemented a call to Dispose in their destructor to Control.

When working in a managed environment, you expect your objects to get automatically garbage collected once you loose all references to them, this includes IDisposable objects. what i know as the best practice is to implement a destructor for all classes implementing the IDisposable interface.

as in microsoft's page on IDisposable interface : http://msdn.microsoft.com/en-us/library/system.idisposable.aspx 

 The IDisposable interface is there to allow you to release resource in case want to force the release of unmanaged resources (and allows you to release managed ones if you really want to) and dont want to wait for the GC to get to your object. 

it was not intended (and generally not used) as a means of unregistering from static events.

-Yossi 

Yossi,

What I believe is happening here is that the various Infragistics controls hook certain static events, such as XPThemeChanged, which will effectively root the control.  If you do not explicitly dispose this control (or the Test object that you're creating), then these static events will not get unhooked, I do not think.  However, the base Component class calls SuppressFinalize in its Dispose method, which means that you will not actually get a call to the finalizer when you dispose this control.  Therefore you will never hit your destructor.  Unless you have a very good reason though it's generally not a recommended .NET practice to use destructors and instead rely on the Dispose implementations.

-Matt 

 i'll add my test's code example to clarify the test i'm running:

 public class Test : UserControl
    {

        public Test()
        {
            Debug.WriteLine("Creating control");
            this.Controls.Add(new UltraTextEditor());
            //this.Controls.Add(new TextBox());
        }
        ~Test()
        {
            Debug.WriteLine("Test destructor called on user control");
        }
    }
    static class Program
    {
        private static void CreateTest()
        {
            Test test = new Test();
            GC.Collect(); //request GC cycle
        }
     
        [STAThread]
        static void Main()
        {
            for (int i=0; i<10; i++)
                CreateTest();

            Debug.WriteLine("Leaving test");
        }
    }

this test outputs:

Creating control
Creating control
Creating control
Creating control
Creating control
Creating control
Creating control
Creating control
Creating control
Creating control
Leaving test

if we comment out the infragistics control and uncomment the TextBox we get:

Creating control
Creating control
Creating control
Test destructor called on user control
Test destructor called on user control
Creating control
Test destructor called on user control
Creating control
Test destructor called on user control
Creating control
Test destructor called on user control
Creating control
Test destructor called on user control
Creating control
Test destructor called on user control
Creating control
Test destructor called on user control
Creating control
Leaving test

-Yossi 

 The usual way this happens is that the call to Dispose (from the IDisposable interface) is supposed to occure when the object gets GCed.

if the interface is implemented on an object that is not a "Control" or "UserControl", then a call has to be made from the destructor to MyObject.Dispose();

For Objects that inherit from "Control", the Control finalizer includes a call to .Dispose()

i.e. if instead of an infragistics control i add a regular windows TextBox, the test i mentiond runs as it should, since the TextBox gets GCed, and the finalizer calls the controls .Dispose() method, after the TextBox is collected, my parent control can be collected as well.

What i suspect is that for some reason Infragistics Controls , or perheps some Controls are somehow still reachable and so they never get GCed, and the Dispose method is never called by the destructor.  

-Yossi.