SevenTV-lib implements 7TV V3 API into easy to use C# library. I'll try to update this library as frequently as possible with new implementations from 7TV side.
var sevenTv = new SevenTV.SevenTV();
SevenTV.Types.User user = await sevenTv.GetUser("60b67e8f561dfc1d80f217c5");
Console.WriteLine(user.username);
More on wiki
You can see examples in EmoteGuesser
SevenTV-lib is using Newtonsoft.JSON to deserialize data from 7TV API.
As SevenTV-lib is written in .NET Standard 2.1 you have to change 'Api Compatibility Level' to .NET 4.x. How to do it