void ctrlDef_OnExecute(NameValueMap Context) { var wpfWindow = new InvAddIn.MyWpfWindow(); // Could be a good idea to set the owner for this window // especially if it was modeless as mentioned in this article: var helper = new WindowInteropHelper(wpfWindow); helper.Owner = new IntPtr(m_inventorApplication.MainFrameHWND); wpfWindow.ShowDialog(); }