class class1 : System.Web.UI.Page  
{  
    private string a
    {
      get{
           if(ViewState["a"] != null)
             return (string)ViewState["a"];
           return "";
         }
      set{
           ViewState["a"] = value;
         }
     }

    public class1()    //构造函数定义  
    {  
        a="你好";  
    }  
    protected void Page_Load(object sender, EventArgs e)  
    {  
        class1 box = new class1();    //初始化sd,并且隐式调用构造函数  
        Response.Write(box.a);  
    }  
}