/upgrade
Upgrades the project file to the latest supported format.
/upgrade
Remarks
If you try to upgrade a CLR project by using vcbuild.exe /upgrade, you will get the following error message:
Cannot upgrade project. Please use 'devenv.exe foo.vcproj /upgrade' to successfully upgrade, or 'vcbuild.exe /upgrade /overrideRefVer foo.
vcproj' to override.
To complete the upgrade using vcbuild.exe, you can specify the /overrideRefVer option. This option will set the MinFrameworkVersion for all assemblies to .NET Framework 3.5.
You can also upgrade the project by using the /upgrade option of devenv.exe. For more information, see /Upgrade (devenv.exe).