how can i selected item in DropDownList (severname) ans i will get all databases names in other DropDownList

List allServer = new List(); List alldatabases = new List(); allServer.Add(new SelectListItem() { Text = "Please Select DataBase...", Value = "", Selected = true }); System.Data.Sql.SqlDataSourceEnumerator instance = System.Data.Sql.SqlDataSourceEnumerator.Instance;

        System.Data.DataTable dt = instance.GetDataSources();
        List<string> ddlInstances = new List<string>();

        foreach (DataRow dr in dt.Rows)
        {

            ServerCoection Co;
            Co = new ServerCoection();
            Co.ServerInstance = string.Concat(dr["ServerName"], "\", dr["InstanceName"]);
            allServer.Add(new SelectListItem() { Text = Co.ServerInstance, Value = Co.ServerInstance, Selected = true });


            Server Ser = new Server(Co);

           foreach (Database db in Ser.Databases)
           {
               alldatabases.Add(new SelectListItem() { Text = db.Name, Value = db.Name, Selected  = false });
           }
        }