binary compability and optional arguments

[endo64]

i made a dll using vb6, it has a function with 2 parameters.
when i add a new optional parameter (i did not change the orders of the parameters) IDE warns me about breaking the compability. I choose the "preserve compability" option, i'm sure that the clients will work with the new parameter without any problem.

but my test application closes itself immediately without giving any error or sometimes windows says "application generated error..." if i put the new version of the dll into the system. It does not give any error like "automation doesn't support method.." or something. if I run the test application from the IDE it works fine, and if recompile it it works fine. but ofcourse i don't want to recompile all the programs which use this dll.

i my opinion it shoud not be problem if a select "preserve compability".
so anybody can explain what is wrong?

[RhinoBull]

...I choose the "preserve compability" option...

Don't where did you find that option ... but you should use "Binary Compatibility".
Do that, recompile your dll and then re-reference it in your main project.
From now on you should be ok for every change you make.

If you you're using test project tp test you dll while in development then use "Project Compatibility" but before compiling change it back to "Binary...".