This is driving me crazy.
I have a rather large project that I am trying to modify. I noticed earlier that when I typed DbCommand, visual studio did
DbCommand
In my case, the @Eliott's answer doesn't work. To solve this problem I had Exclude/Include From Project my deficient file, andalso Clean and Rebuild the solution.
After these actions, my file with my last modifications and the debugger are restored.
I hope this help.