asp.net 动态创建控件和移除控件

废话不多说 直接看一个小demo 

前台代码

 <form id="form1" runat="server">
    <div>
        <asp:Panel ID="pnlAdd" runat="server">
            <asp:CheckBox ID="CheckBox1" runat="server" />
            <!-- 制定动态控件的位置 -->
           <placeholder id="p1" runat="server"></placeholder>
            <asp:Calendar ID="Calendar1" runat="server">
            </asp:Calendar>
        </asp:Panel>
    <hr />
        <asp:Button ID="btnCreate" runat="server" Text="CreateControl" 
            onclick="btnCreate_Click" />
        <asp:Button ID="btnRemove" runat="server" Text="RemoveContrel" 
            onclick="btnRemove_Click" />
    </div>
    </form>

后台代码

 Button btn1 = null;
        //PlaceHolder p1 = new PlaceHolder();
        protected void Page_Load(object sender, EventArgs e)
        {