I am working on a large scale project where a custom (pretty good and robust) framework has been provided and we have to use that for showing up forms and views.

There is abstract class StrategyEditor (derived from some class in framework) which is instantiated whenever a new StrategyForm is opened.

StrategyForm (a customized window frame) contains StrategyEditor.
StrategyEditor contains StrategyTab.
StrategyTab contains StrategyCanvas.

This is a small portion of the big classes to clarify that there are many objects that will be created if one StrategyForm object is allocated in memory at run-time. My component owns all these classes mentioned above except StrategyForm whose code is not in my control.

Now, at run-time, user opens up many strategy objects (which trigger creation of new StrategyForm object.) After creating approx. 44 strategy objects, we see that the USER OBJECT HANDLES (I'll use UOH from here onwards) created by the application reaches to about 20k+, while in registry the default amount for handles is 10k. Read more about User Objects here. Testing on different machines made it clear that the number of strategy objects opened is different for message to pop-up - on one m/c if it is 44, then it can be 40 on another.

When we see the message pop-up, it means that the application is going to respond slowly. It gets worse with few more objects and then creation of window frames and subsequent objects fail.

We first thought that it was not-enough-memory issue. But then reading more about new in C# helped in understanding that an exception would be thrown if app ran out of memory. This is not a memory issue then, I feel (task manager also showed 1.5GB+ available memory.)

M/C specs
Core 2 Duo 2GHz+
4GB RAM
80GB+ free disk space for page file
Virtual Memory set: 4000 - 6000


My questions

Q1. Does this look like a memory issue and I am wrong that it is not?
Q2. Does this point to exhaustion of free UOHs (as I'm thinking) and which is resulting in failure of creation of window handles?
Q3. How can we avoid loading up of an StrategyEditor object (beyond a threshold, keeping an eye on the current usage of UOHs)? (we already know how to fetch number of UOHs in use, so don't go there.) Keep in mind that the call to new StrategyForm() is outside the control of my component.
Q4. I am bit confused - what are Handles to user objects exactly? Is MSDN talking about any object that we create or only some specific objects like window handles, cursor handles, icon handles?
Q5. What exactly cause to use up a UOH? (almost same as Q4)

I would be really thankful to anyone who can give me some knowledgeable answers. Thanks much! :)