ClaimsExtensions.cs

using System.Linq;
using System.Security.Claims;
using Newtonsoft.Json;

namespace Account
{
    public static class ClaimsExtensions
    {
        public static string Get(this ClaimsIdentity identity, string type)
        {
            return identity.Claims.FirstOrDefault(p => p.Type == type)?.Value;
        }

        public static T Get<T>(this ClaimsIdentity identity, string type) where T : new()
        {
            var json = identity.Claims.FirstOrDefault(p => p.Type == type)?.Value;
            return json == null ? new T() : JsonConvert.DeserializeObject<T>(json);
        }

        public static void Set(this ClaimsIdentity identity, string type, string value)
        {
            identity.AddClaim(new Claim(type, value));
        }

        public static void Set<T>(this ClaimsIdentity identity, string type, T obj)
        {
            var json = JsonConvert.SerializeObject(obj);
            identity.AddClaim(new Claim(type, json));
        }
    }
}