static async void Main(string[] args) { await Task.Run(() => { var classInfo = new List<ClassInfo>() { new ClassInfo() { Id = 1, Name_employee = "Лозан С.Л." }, new ClassInfo() { Id = 2, Name_employee = "Курах Є.О." }, new ClassInfo() { Id = 3, Name_employee = "Власюк О.І." }, new ClassInfo() { Id = 4, Name_employee = "Маргітич О.В." }, new ClassInfo() { Id = 5, Name_employee = "Сливка І.І." }, }; var info = new List<Info>() { new Info() { Name_employee = "Лозан С.Л.", Workplace_address = "Берегівська ЗОШ", The_presence_of_diphtheria_vaccination = "Вакцинована" }, new Info() { Name_employee = "Курах Є.О.", Workplace_address = "Берегівська ЗОШ", The_presence_of_diphtheria_vaccination = "Вакцинований" }, new Info() { Name_employee = "Власюк О.І.", Workplace_address = "Берегівська ЗОШ", The_presence_of_diphtheria_vaccination = "Вакцинований" }, new Info() { Name_employee = "Маргітич О.В.", Workplace_address = "Берегівська ЗОШ", The_presence_of_diphtheria_vaccination = "Не вакцинована" }, new Info() { Name_employee = "Сливка І.І.", Workplace_address = "Берегівська ЗОШ", The_presence_of_diphtheria_vaccination = "Не вакцинований" } }; var c = info[1]; var infor = info .Join(classInfo, c => c.Name_employee, n => n.Id, (c, n) => new { Name_employee = c.Name_employee, Workplace_address = n.Name_employee, The_presence_of_diphtheria_vaccination = c.The_presence_of_diphtheria_vaccination }); Console.WriteLine(Newtonsoft.Json.JsonConvert.SerializeObject(info)); Console.ReadKey(); } }