Visual Studio LightSwitch - How to show something other than text in a tooltip?

I have two image properties in my entity: Thumbnail a开发者_如何转开发nd HiResPhoto, and I am showing Thumbnail in a grid. How can I show HiResPhoto as a ToolTip for the Thumbnail image displayed in the grid?

This is currently not possible. One needs to build a user control and use it instead of the built-in image control. And then you have whatever you want as a tooltip.