C# Linq 去重

        static void Main(string[] args)
        {
            var list = new List<roleJson>() {
            new roleJson(){ Id=1,RoleName="1",IsUsed="1" },
            new roleJson(){ Id=1,RoleName="1",IsUsed="1" },
            new roleJson(){ Id=2,RoleName="2",IsUsed="2" },
            new roleJson(){ Id=3,RoleName="3",IsUsed="3" },
            };

            list = list.GroupBy(t => t.Id).Select(x => x.First()).ToList();

            Console.WriteLine();
            Console.ReadLine();
        }