C# winform combobox 在绑定数据之后插入一项选择项

       /**//// <summary>
        /// 填充comboboxB超医师 geovindu@163.com 涂聚文
        ///2009-02-16
        /// </summary>
        private void setDBPyhNameComboBox()
        {

            this.combPhy.DataSource = null;

            DBConnectioin dbc = new DBConnectioin();
            SqlConnection conn = new SqlConnection(DBConnectioin.conStr);
            conn.Open();
            //DbHelperSQL.setComboList(combPhy, "select PhyID,PhyName  from Physician", "Physician", "PhyName", "PhyID");
            string sSQL = "select PhyID,PhyName  from Physician";
            string sTable = "Physician";

 
            DataSet dsCourtesy = new DataSet();
            SqlDataAdapter daCourtesy = new SqlDataAdapter();
            DbHelperSQL.setCommand(dsCourtesy, daCourtesy, sSQL, sTable);
            daCourtesy.Fill(dsCourtesy);
            combPhy.DataSource = dsCourtesy.Tables[0].DefaultView;              
            DataRow dr = dsCourtesy.Tables[0].NewRow();
            combPhy.DisplayMember = "PhyName";
            combPhy.ValueMember = "PhyID";            
            dr["PhyName"] = "全部";  
            dr["PhyID"] = -1;  
            dsCourtesy.Tables[0].Rows.InsertAt(dr, 0);
            //combPhy.Text = "全部";


        }

默认让combobox选择一项

comboBox.SelectIndex = 0