设置DropDownList的当前选项

            myCommand.Fill(ds, "tb_role");
            DataView dv = ds.Tables["tb_role"].DefaultView;    
            if (ds.Tables["tb_role"].Rows.Count !=0) //如果表不空,绑定数据
            {                    
                rbtl_role.DataSource=ds.Tables["tb_role"].DefaultView;    
                rbtl_role.DataTextField = "rolename";
                rbtl_role.DataValueField = "roleid";                                       
                rbtl_role.DataBind();             
            }
            //对RadioButtonList进行哈稀编号，保持同RadioButtonList.SelectedIndex的值一致编号
            int i = 0;
            foreach(DataRowView drv in dv )
            {
            StateIndex[drv.Row["roleid"]]=i;                
                i++;
            }
            //进行比较，对选中的进行设置
            sql = "select roleid from tb_userrole where user_id=1";    
            OleDbCommand myCmd = new OleDbCommand(sql, myConnection); 
               myConnection.Open();