如何使用拇指使WPF弹出窗口可拖动？

I've searched long and hard to find an example of this on the net. I've seen the alternative methods for this but I want to specifically use a thumb. In trying to hash out a solution I've been unable to get the functionality right/working as I'm fairly new to WPF. I'd be grateful if someone could give an example of how you may implement the above.I've searched long and hard to find an example