///
 /// 國籍的接口
 ///
 public interface INationality
 {
     string Nationality
     {
         set;
         get;
     }
     string GetNationality();
 }

  ///
  /// 中國人
  ///
  public class Chinese : INationality
  {
      private string _Nationality;
      public string Nationality
      {
          set
         {
             _Nationality = value;
         }
     }

     public string GetNationality()
     {
         return string.IsNullOrEmpty(_Nationality) ? "Default." : _Nationality;
     }
 }
 ///
 /// 美國人
 ///
 public class American : INationality
 {
     private string _Nationality;
     public string Nationality
     {
         set { _Nationality = value; }
     }

     public string GetNationality()
     {
         return string.IsNullOrEmpty(_Nationality) ? "Default." : _Nationality;
     }
 }

  ///
  ///
  ///

  ///
  public class PrintNationality where T : INationality, new()
  {
      T item = new T();
      public void Print()
      {
         Console.WriteLine(string.Format("Nationality:{0}", item.GetNationality()));
      }
  }

  public class Program
  {
      static void Main(string[] args)
      {
          PrintNationality _c = new PrintNationality();
          PrintNationality _a = new PrintNationality();
          //PrintNationality _o = new PrintNationality(); 此句是錯誤的，因為泛型類型必須是繼承自INationality接口的類
          _c.Print();
          _a.Print();
         Console.ReadKey();
     }
 }