Question

Currently developing a connector DLL to HP s Quality Center. I m using their (insert expelative) COM API to connect to the server. An Interop wrapper gets created automatically by VStudio.

My solution has 2 projects: the DLL and a tester application - essentially a form with buttons that call functions in the DLL. Everything works well - I can create defects, update them and delete them. When I close the main form, the application stops nicely.

But when I call a function that returns a list of all available projects (to fill a combo box), if I close the main form, VStudio still shows the solution as running and I have to stop it.

I ve managed to pinpoint a single function in my code that when I call, the solution remains "hung" and if I don t, it closes well. It s a call to a property in the TDC object get_VisibleProjects that returns a List (not the .Net one, but a type in the COM library) - I just iterate over it and return a proper list (that I later use to fill the combo box):

    public List<string> GetAvailableProjects()
    {
        List<string> projects = new List<string>();
        foreach (string project in this.tdc.get_VisibleProjects(qcDomain))
        {
            projects.Add(project);
        }
        return projects;
    }

My assumption is that something gets retained in memory. If I run the EXE outside of VStudio it closes - but who knows what gets left behind in memory?

My question is - how do I get rid of whatever calling this property returns? Shouldn t the GC handle this? Do I need to delve into pointers?

Things I ve tried:

getting the list into a variable and setting it to null at the end of the function
Adding a destructor to the class and nulling the tdc object
Stepping through the tester function application all the way out, whne the form closes and the Main function ends - it closes, but VStudio still shows I m running.

Thanks for your assistance!

Answer 1

Try to add these 2 lines to post-build event:

call "$(DevEnvDir)..Toolsvsvars32.bat"
editbin.exe /NXCOMPAT:NO "$(TargetPath)"

Answer 2

Have you tried manually releasing the List object using System.Runtime.InteropServices.Marshal.ReleaseComObject when you are finished with it ?

Answer 3

I suspect some dangling threads.

When this happens, pause the process in the debugger and see what threads are still around.

Answer 4

May be try to iterate the list manually using it s count and Item properties instead of using it s iterator, some thing like:

for (int i=1; i <= lst.Count ; ++i)
{
 string projectName = lst.Item(i);
}

It might be the Iterator that keeps it alive and not the list object itself, if not using an iterator might not have a problem.

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