Was working on a new solution, new project in Visual Studio 2012 Express for Web. For some reason, the tooltip info that normally appears for variables and objects when I hit a breakpoint while debugging is no longer working, even for my older solutions/projects that used to work fine. The breakpoints work fine, but no info at all appears when I hover over variables, etc.
Have no idea if this has anything to do with it, but I did set this new solution/project to ASP 4.5.
Repairing Visual Studio did not work. I uninstalled and reinstalled Visual Studio. My problem now seems to be resolved.
来源：https://stackoverflow.com/questions/17309752/hover-tooltip-stopped-working-in-visual-studio-2012-express-for-web