高手指点一下啊 ，弄了好长时间没搞好

<asp:RadioButton ID= "rdoGZ " runat= "server " GroupName= "rdoCity " Text= "广州 " Checked= "True " OnCheckedChanged= "rdoGZ_CheckedChanged " />
  <asp:RadioButton ID= "rdoSZ " runat= "server " GroupName= "rdoCity " Text= "深圳 " OnCheckedChanged= "rdoSZ_CheckedChanged " />
<asp:DropDownList ID= "ddltSanjak " runat= "server ">


为什么如上的radiobutton不能触发如下的事件：

protected void rdoSZ_CheckedChanged(object sender, EventArgs e)
{
InitddltSanjak();
}
protected void rdoGZ_CheckedChanged(object sender, EventArgs e)
{
Response.Write( "ggg ");
}

[解决办法]
将rdoGZ的AutoPostBack属性设为True。