If you have not removed your MainWindow.xaml then use this way :- var mainWindow = new MainWindow(); if you have, then create a window but under Views folder with this name MainView.xaml and then go about it way this video is telling you.

I have update code to fix this issue private bool dragging = false; private Point startPoint = new Point(0, 0); private void panelTitleBar_MouseDown(object sender, MouseEventArgs e) { //ReleaseCapture(); //SendMessage(this.Handle, 0x112, 0xf012, 0); dragging = true; startPoint = new Point(e.X, e.Y); } private void panelTitleBar_MouseMove(object sender, MouseEventArgs e) { if (dragging) { Point p = PointToScreen(e.Location); Location = new Point(p.X - this.startPoint.X, p.Y - this.startPoint.Y); } } private void panelTitleBar_MouseUp(object sender, MouseEventArgs e) { dragging = false; }