<p>I am trying to get center of parent form, not center of screen behavior.
Passing in the parent form seems to only control the ownership of the window.
These classes are sealed, so I do not see how I can do any WinProc tricks.
Rewriting the classes is not an appealing option.
Any other ideas?</p>

I do not know much about the dialogs or message boxes but, you can position a new Form as you are looking for with its StartPosition property.
```
```
System.Windows.Forms.Form f = new Form();
f.StartPosition = FormStartPosition.CenterParent;
```
```