I have a SharePoint 2013 solution migrated from VS 2010 and SharePoint 2010 which gives me an upgrade report every time it loads in VS 2012. I have not opened it with VS 2010 in the mean time. Also, all the source code files are write protected so I consistently have to deal with forcing overwrites and things of that nature. Originally the solution was bound to Vault source control, but I removed the bindings prior to upgrading because we're also switching to Team Foundation Server 2012. Presently the 2012 version of the solution should not be bound to any source control. Only one project out of the 8 in the solution is having this issue.
Migration Report message:
Visual Studio needs to make non-functional changes to this project in order to enable the project to open in this version and Visual Studio 2010 SP1 without impacting project behavior
Is this potentially due to the project file being write protected? Is there some manual way I can edit the project file and prevent this in the future?
I'm not sure why Visual Studio 2012 can't deal with the upgrade properly, but I've found the workaround. Edit your .CSPROJ file(s) and look for this line:
<FileUpgradeFlags>0</FileUpgradeFlags>
Remove the contents of that node so it's empty:
<FileUpgradeFlags></FileUpgradeFlags>
Visual Studio will no longer attempt to upgrade the projects every time. For the record, I've only ever seen this behavior when upgrading a SharePoint 2010 project using VS 2012. Other types of projects seem to be okay.
来源：https://stackoverflow.com/questions/16362244/visual-studio-2012-keeps-showing-upgrade-report