4.placeholder 容器控件，不会产生任何客户端代码
 textbox等集合类的使用：
 public class textboxArray:system.collection.collectionbase
 {
  private readonly system.web.control hostpage;
  public textboxArray(system.web.control host)
  {
   hostpage = host;
  }
  public void AddNewTextBox()
  {
   TextBox atextbox = new TextBox();
   this.List.Add(atextbox);
   hostpage.controls.add(atextbox);
   atextbox.style["left"] = Convert.ToString((count-1)*130+70);
   atextbox.style["top"] = Convert.ToString(160);
   atextbox.width = 120;
   atextbox.borderstyle = boderstyle.outset;
   atextbox.id = this.count.ToString();

   atextbox.text = "textbox示例";
   atextbox.forecolor = sytem.drawing.color.blue;
  }
  //创建索引
  public TextBox this[int index]
  {
   get
   {
    return (TextBox)this.List[index];
   }
  }
  //remove方法来删除控件
  public void remove()
  {
   if(this.count>0)
   {
    hostpage.controls.remove(this[this.count-1]);
    this.List.removeAt(this.count-1);
   }
  }
 }
5.添加控件事件:
 Button btn1 = new Button("click me");
 btn1.CommandArgument = "btn1";
 btn1.Command += new CommandEventHandler(this.OnButton);
 ph.controls.add(btn1);
 下面事件函数:
 public void OnButton(object sender,CommandEventArgs e)
 {
  ---------normal
 }
  
 Control c3 = ParseControl("<asp:button id='btn2' text='click btn2' CommandName='btn' CommangArgument='b2' runat='server'></asp:button>");
 Button btn3 = (Button)page.FindControl("btn2");
 btn3.Command += new CommandEventHandler(this.OnButton);
 事件函数变为:
 public void OnButton(object sender,CommandEventArgs e)
 {
  switch(e.CommandArgument.Tostring().toLower())
  {
   case "btn1":
   case "b2":
  }
 }