Nuget 2.7 Error – Input string was not in a correct format

Nuget 2.7 Error – Input string was not in a correct format

I recently installed a fresh copy of Visual Studio 2013 with Nuget 2.7. Shortly afterward I began installing a few Packages, which appeared to occur without a problem. It wasn’t until I began coding against those libraries that I noticed something wasn’t right. The libraries did not show under references although they showed up under Nuget Package Manager. I tried removing the Packages which generated the following error.

Installing 'TopShelf 3.1.2'. 
Successfully installed 'TopShelf 3.1.2'. 
Adding 'log4net 2.0.0' to Cogs.Server. 
Install failed. Rolling back... 
install-package : Input string was not in a correct format. 
At line:1 char:1
install-package topshelf
~~~~~~~~~~~~~~~~~~~~~~~
CategoryInfo : NotSpecified: (:) [Install-Package], FormatException
FullyQualifiedErrorId : NuGetCmdletUnhandledException,NuGet.PowerShell.Commands.InstallPackageCommand

Apparently this is a known bug in Nuget 2.7. The solutions I found were either to uninstall 2.7 and install a previous version, or run the following command to register a COM object.

regsvr32 "C:\Program Files (x86)\Common Files\microsoft shared\MSEnv\VsLangproj.olb"

While manually registering a COM object doesn’t seem the cleanest fix, it does seem to fix it. After running this I no longer had any issues installing/uninstalling Packages. I also had been getting sporadic Visual Studio crashes when the Nuget Package Manager screen was open, and those went away as well.

One footnote, I had to go back and manually clean up the Packages I had installed prior, but had not fully installed. What I did was open the packages.config for each project and remove the existing Package reference, then reinstall the Package. After that everything seemed to work as expected.