These are the few top solutions for getting Visual Studio 2012 intellisense back on track try them one by one, hope one of them will solve the problem:
When the problem occurs next time follow these:
start from #1 and Move to next when the earlier one doesn't work for you
1: Close all the tabs
and open your file again. (Thanks to russds)
2: Clean the Build
> Close the Solution
> Restart Visual Studio
> Open the Solution
again
3: Goto: Edit
> IntelliSense
> Refresh Local Cache
4: Close Visual Studio 2012 and delete this folder: %AppData%\Microsoft\VisualStudio\11.0\ReflectedSchemas
5: Goto: TOOLS
> Import and Export Settings
> Reset all settings
6: Delete .suo
file in the project folder. (Thanks to Jason Steele)
I am hopeful your problem will get solved by any of the above six steps.
But if it doesn’t after all this than I think you should consider reinstalling your VS2012.
Ctrl
+Space
works after this problem appears? – SajjadHashmi