WPF：如何在Canvas中安装拇指行为？

I would like to have a Canvas that supports the DragDelta event. My first idea of how to do this was to make a ControlTemplate that includes a thumb. But I do not know how to do this correctly. How can I change the XAML below to make it compile, and what's the right way to install the DragDelta event handler?I would like to have a Canvas that supports the