Question

I created a COM Visible DLL in C# that should show a Form after some inputs from the User in the host application (unmanaged). It works fine with ShowDialog(), but ideally the Form should keep running even after the DLL finishes. Because the Form need some Data a separated Project with Main(string[] args) is not an option.

How can I accomplish this? I tried something like that but it didn’t worked.

public class FormManager : ApplicationContext
{
    FormMain frmMain;


    public FormManager()
        :base(new FormMain())
    {
        frmMain = (FormMain)this.MainForm;
        frmMain.Closed += new EventHandler(OnFormClosed);
    }

    public void SetData(object o1, object o2)
    {
        if (frmMain != null)
        {
            frmMain.SetData(o1, o2);
            frmMain.Show();
        }
    }

    private void OnFormClosed(object sender, EventArgs e)
    {
            ExitThread();
    }
}

I have no idea where Application.Run should be inserted.

Answer 1

I, too, am a little unclear as to what exactly you are trying to do here… but normally, if you are placing the Application.Run somewhere in that code, it would be in place of this line:

frmMain.Show();

Of course, by using Application.Run you will be freezing this code (the thread that calls Application.Run) until the form in question closes… So maybe that doesn’t really accomplish what you want (it is, indeed, unclear).

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Edit After Clarification of Question

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Here’s the thing about COM in .NET that was not true about previous iterations of Microsoft languages. When you call an assembly in .NET via COM (OLE) the calling assembly subsumes the COM exposed code into its runtime. In other words, when you look in the Task Manager, you won’t see both of your assemblies running! You’ll only see the one that did the calling. Thus, when you close the main assembly, you close any running code attached to it, including your COM code.

There is one way around this, but it’s not simple. In short, you would need to:

1. Launch your second process (you could, for instance, use a Process.Start())
2. Use the first process to look inside the ROT (Running Objects Table) and locate the second assembly
3. Communicate freely via COM (OLE) and pass your data

At this point, the two assemblies are running in separate runtimes, which will allow you to produce forms in the second assembly that will not close when the first assembly closes. That, as I understand it, is what you’re looking for.

If you want to try this route, do a little Googling for the ROT and try some sample code. If you have questions about that let me know!