It's a bug happened when you've installed vs in some place other than default location. This version of vsix haven't make the extension.vsixmanifest right.
open file C:\Program Files (x86)\Microsoft Visual Studio 14.0\Common7\IDE\Extensions\Microsoft\CodeContracts\1.9.10714.2\extension.vsixmanifest in notepad, change the <Identity Version="" to right version.
Current package seems to have a problem with Visual Studio 2015. VS does not start after this package is installed. The splash screen comes up and then it goes away and the process is gone. The error received is 'No InprocServer32 registered for package [Async Query Service Package]'. A repair install of VS is required to fix.
UPDATED It is a perfect tool in speaking of function. However, I also have the same problem that although 1.9.10714.2 is installed (on Visual Studio 2015). VS still tell me it needs to be updated from version 1.8.
I found following steps would work around.
1. After install the extension, open and close VS.
3.Within following 4 folders 1.C:\Program Files (x86)\Microsoft Visual Studio 11.0\Common7\IDE\Extensions\Microsoft\CodeContracts\1.9.10714.2 2. C:\Program Files (x86)\Microsoft Visual Studio 12.0\Common7\IDE\Extensions\Microsoft\CodeContracts\1.9.10714.2 3.C:\Program Files (x86)\Microsoft Visual Studio 14.0\Common7\IDE\Extensions\Microsoft\CodeContracts\1.9.10714.2 4.C:\VS10Root\Common7\IDE\Extensions\Microsoft\CodeContracts\1.9.10714.2
4. There is one file named extension.vsixmanifest in each of above 4 directory. Open it with notepad.
5. make sure in each of three file, on line 4, the value of Identity version is 1.9.10714.2. If not, change it to 1.9.10714 and save the change.
6. Restart VS two times, first time it still tell you to upgrade, but second time and afterwards it's OK.
Many users are complaining about several bugs, including a wrong version numbers and some bugs that prevent to use "Emit contracts into XML doc file" in VS2015, and more than two months after the last release v1.9.10714.2 we still get no fix?
Static analyzer is not working stable in VS2015. Uninstall does not work properly. Extensions stays in the VS 2015 Extensions list. After unable to uninstall addon properly VS 2015 freezes on Debug and requires full reinstall.
Please fix the version information so the plugin does not show up for updates after you have updated. After installing 1.9 the Extensions window still thinks I'm running 1.8.... (happens on all VS installations)
The version problem is due to old version information within the extension manifest files within the package. After installing, I modified the version field for Visual Studio 2015 to fix the problem on my machine.