Converting JWT (json Web token) into key value pairs in WebAPi

I can access jwt inside my web api action by accessing it's Autorization Header

string jwt=Request.Headers.Authorization.ToString();
string jwtArray = jwt.split('.');

//Now i want to convert it's payload into Key value pair.

The payload is in jwtArray[1]. Can anyone suggest how this can be converted into a KVP. I am assuming the JWT is Base64 encoded by the look of it.