1 ///<summary>
 2 /// 国籍的接口
 3 ///</summary>
 4 public interface INationality
 5 {
 6     string Nationality
 7     {
 8         set;
 9         get;
10     }
11     string GetNationality();
12 }

 1 ///<summary>
 2 /// 中国人
 3 ///</summary>
 4 public class Chinese : INationality
 5 {
 6     private string _Nationality;
 7     public string Nationality
 8     {
 9         set
10         {
11             _Nationality = value;
12         }
13     }
14 
15     public string GetNationality()
16     {
17         return string.IsNullOrEmpty(_Nationality) ? "Default." : _Nationality;
18     }
19 }
20 
21 ///<summary>
22 /// 美国人
23 ///</summary>
24 public class American : INationality
25 {
26     private string _Nationality;
27     public string Nationality
28     {
29         set { _Nationality = value; }
30     }
31 
32     public string GetNationality()
33     {
34         return string.IsNullOrEmpty(_Nationality) ? "Default." : _Nationality;
35     }
36 }

 1 ///<summary>
 2 ///
 3 ///</summary>
 4 ///<typeparam name="T"></typeparam>
 5 public class PrintNationality<T> where T : INationality, new()
 6 {
 7     T item = new T();
 8     public void Print()
 9     {
10         Console.WriteLine(string.Format("Nationality:{0}", item.GetNationality()));
11     }
12 }

 1 public class Program
 2 {
 3     static void Main(string[] args)
 4     {
 5         PrintNationality<Chinese> _c = new PrintNationality<Chinese>();
 6         PrintNationality<American> _a = new PrintNationality<American>();
 7         //PrintNationality<Object> _o = new PrintNationality<Object>(); 此句是错误的，因为泛型类型必须是继承自INationality接口的类
 8         _c.Print();
 9         _a.Print();
10         Console.ReadKey();
11     }
12 }