DataGrid模版中嵌入了dropdownlist,如何触发这个dropdownlist的事件

protected void ddlChange(object sender, System.EventArgs e)
{
TextBox1.Text = "111";
}

private void DataGrid1_ItemCreated(object sender, System.Web.UI.WebControls.DataGridItemEventArgs e)
{
if(e.Item.ItemType==ListItemType.Item || e.Item.ItemType==ListItemType.AlternatingItem)
{
DropDownList ddl = (DropDownList)e.Item.FindControl("DropDownList2");
ddl.SelectedIndexChanged+=new System.EventHandler(this.ddlChange);
}
}