xCAD framework allows to show custom Windows Form and WPF Window as a popup window.

Framework will automatically assign SOLIDWORKS window as a parent window for the forms.

var winFormPopupWnd = this.CreatePopupWindow<WinForm>();
winFormPopupWnd.ShowDialog();

var wpfPopupWnd = this.CreatePopupWindow<WpfWindow>();
wpfPopupWnd.ShowDialog();