What's the reason for error message? I am using VS 2010 professional edition

Solution 1:

It happened to me with VS2012 as well after loading the project without source control binding, a local simple WinForms project. All I needed to do was Clean & Rebuild. After that the problem was solved.

Solution 2:

This is a bug in Visual Studio. According to http://connect.microsoft.com/VisualStudio/feedback/details/742959/the-snapshot-is-out-of-date "We've taken a closer look at this problem and it isn't one that we'll be able to solve in the next release of Visual Studio."

They recommend waiting around until the background language parser service is done (or, in other words, don't try to be too productive there partner.) My experience is that closing all documents, cleaning the solution, rebuilding it and then closing and re-opening with a pause after does remove the error.

Until you do something silly, like edit code. Then all bets are off again as to when it reoccurs.