Convert JWT (JSON Web Token) to JSON in ASP.Net

I have function return string as Encoded access token when success login

user.AccessToken=GenerateTokens();

How to return Jwt as jsonresult before encoding from function GenerateTokens();

and put result in user.AccessToken as json

meaning i need to assign jwt variables before converted by JwtSecurityTokenHandler().WriteToken as json and assign it to

user.AccessToken=GenerateTokens();

        public string GenerateTokens(string userId)
        { 
            var Claims = new Claim[]{
                new Claim(JwtRegisteredClaimNames.Sub,userId)
            };
            var signingkey = new SymmetricSecurityKey(Encoding.UTF8.GetBytes("Engaz@2012"));
            var SigningCredntials = new SigningCredentials(signingkey, SecurityAlgorithms.HmacSha256);
            var Jwt = new JwtSecurityToken();
            var jsonu = new { id = userId };
            Jwt.Payload["user"] = jsonu;           
          
            return new JwtSecurityTokenHandler().WriteToken(Jwt);
        }
        public class Users
        {
            public dynamic AccessToken{ get; set; }
        }