Drag a Line and draw in another else...

Question

sorry, but i just study C# , and i have many problems with this language..im  doing  a exercise about draw a line in form . My teacher require me to design a face which user can use mouse to drag a point from here to another else...after draw this line in a new place(each time mouse move)...my teacher show me to use method drag and drop in C# , but i don't know how to do that... so , has anybody here can help me....thank in advance!