<t>I had the same error (missing exactly the same package) today. I also created a MVC + Web API project.<br/>
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It happened because I moved the app files (including the .csproj) file to another location. I manually updated the .sln file but all packages dependencies are now (Visual Studio 2015) stored in .csproj file.<br/>
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Editing the .csproj file and correcting the relative path to the solution folder (which contains the packages folder) solved the problem for me.</t>
