//get the selected data by JS
var select = document.getElementById('SCountry');
alert(select.options[select.selectedIndex].innerText); //selected text
alert(select.options[select.selectedIndex].value); //selected value
//clear the binding data
DropDownList.Items.Clear();
DropDownList.Items.Remove(item);
//add item
DropDownList.Items.Add("AP");
//insert
DropDownList.Items.Insert(0, new ListItem("", "0"));