Introduction to where generic constraints in C#

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

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

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