DropDownList选择改变时怎么触发服务端事件

DropDownList选择改变时如何触发服务端事件？
DropDownList选择改变时如何触发服务端事件？

[解决办法]
private void DropDownList1_SelectedIndexChanged(object sender, System.EventArgs e)
{
this.Page.RegisterStartupScript( "aa ", "要执行的脚本函数; ");
}
[解决办法]
private void DropDownList1_SelectedIndexChanged(object sender, System.EventArgs e)
{
this.Page.RegisterStartupScript( "aa ", " <script language=javascript> alert( 'aaaaa '); </script> ");
}