[原创]给Asp.Net初学者的关于继承和多态性的例子[2]

   sw.writeline("lastname:"+_lastname.tostring());
   sw.writeline("phone:"+_phonenumber.tostring());
   sw.flush();
   sw.close();
   fs.close();
  }
}
 
  public class extendedprofile:profile        建立profile子类extendedprofile，他可以继承profile中的方法
  {
    protected string _address1;                  //子类extendedprofile的属性
    protected string _address2;
    protected string _city;
    protected string _state;
    protected string _postal;
    protected string _description;
 
 public extendedprofile()                      //子类extendedprofile中属性的初始值
 {
   _address1 = "清华大学";
   _address2 = "清华大学物理实验室";
   _city = "北京";
   _state = "北京";
   _postal = "100024";
   _description = "教授";
 }
 
 public override void setphonenumber(string phonenumber)           //继承类profile中的setphonenumber()方法
 {                                                                                                 //setphonenumber()方法的重载
   _phonenumber = phonenumber;
 }
 
 public string getaddress1()          //子类extendedprofile中的方法getaddress1()，以下类推
 {
   return _address1;
 }
 public string getaddress2() 
 {
   return _address2;
 }
 public void setaddress(string address1,string address2)
 {
   _address1 = address1;
   _address2 = address2;
 }
 
 public string getcity()
 {
   return _city;
 }
 public void setcity(string city)
 {
   _city = city;
 }
 
 public string getstate()
 {
   return _state;
 }
 public void setstate(string state)
 {
   _state = state;
 }
 
 public string getpostal()
 {
   return _postal;
 }
 public void setpostal(string postal)
 {
   _postal = postal;
 }
 
 public string getdescription()
 {
   return _description;
 }
 public void setdescription(string description)
 {
   _description = description;
 }
 
 public override void save()                //调用接口isavedata()中的方法save()，save()方法的重载，由于多态性
 {                                                       //子类extendedprofile可以自定义并修改save()方法
   string _document = "d:\\myweb2\\saidy.xml";
   xmltextwriter writer = null;           //保存为一个xml文件
   try
   {
    writer = new xmltextwriter(_document,null);
    writer.formatting = formatting.indented;
    writer.writestartdocument(false);
    writer.writedoctype("profile",null,null,null);            //表示<!doctype profile>
    writer.writestartelement("profile");                         //生成根元素  
    writer.writeelementstring("firstname",_firstname);   //生成子元素  <firstname>_firstname</firstname>
    writer.writeelementstring("lastname",_lastname);