As well as demonstrating how to create a simple Tooltip control for your application, this project shows how to get/set the absolute position of a control in your application even if it is not a Canvas control.
for complete details of this project visit
http://silverlighttips.com/?tag=/tooltip.
Please note that Silverlight 3.0 has a built in tooltip feature, however I have created this project to demonstrate hot to use your xaml with all it's controls and layout as a tooltip, and more importantly how to adjust the position of this xaml manually according to your design and layout. This could be helpful if you want to position a control (i.e. Grid) from the code.