because NuGet Package Manager (Version 2.8.60318.667) for VS 2012 does not support .NETStandard (Used for Latest Newtonsoft Json Parser Lib.
https://github.com/NuGet/Home/issues/3131
I resolve this issue by installing older version of Newtonsoft Json:
PM> Install-Package Newtonsoft.Json -Version 9.0.1
More details on:
https://github.com/NuGet/Home/issues/5162
.