1     public class STU
2     {
3         public int ID { get; set; }
4         public string Name { get; set; }
5         public int Age { get; set; }
6         public string City { get; set; }
7     }

1             List<STU> stuList = new List<STU>()
2             {
3                 new STU{ID=1,Name="Lily",Age=18,City="NewYork"},
4                 new STU{ID=2,Name="Lucy",Age=20,City="NewYork"},
5                 new STU{ID=1,Name="LiLei",Age=18,City="BeiJIng"}
6             };

1             foreach (IGrouping<string,STU> group in stuList.GroupBy(c=>c.City))
2             {
3                 Console.WriteLine("当前的城市为" + group.Key);
4                 foreach (STU stu in group.OrderBy(a=>a.Age))
5                 {
6                     Console.Write(stu.Name+";");
7                 }
8                 Console.WriteLine();
9             }