class Program    {        static void Main(string[] args)        {            var listTest1 = new List<Test1>            {                new Test1{Key="1",Name="1"},                new Test1{Key="2",Name="2"},                new Test1{Key="3",Name="3"}            };            var listTest2 = new List<Test2>            {                new Test2{SubKey="sub1",SubName="sub1",MainKey="1",},                new Test2{SubKey="sub2",SubName="sub2",MainKey="2"},                new Test2{SubKey="sub3",SubName="sub3",MainKey="2"}            };            var result = from t1 in listTest1                         join t2 in listTest2                         on t1.Key equals t2.MainKey                         select new TestResult(t1, t2);            result = result.ToList();            Console.WriteLine(result);            Console.ReadKey();        }    }    public class Test1    {        public string Key { get; set; }        public string Name { get; set; }    }    public class Test2    {        public string SubKey { get; set; }        public string SubName { get; set; }        public string MainKey { get; set; }    }    public class TestResult    {        public string Name { get; set; }        public string SubName { get; set; }        public TestResult(Test1 t1, Test2 t2)        {            this.Name = t1.Name;            this.SubName = t2.SubName;        }    }