private void Form1_Load(object sender, EventArgs e)
        {

            OracleConnection con1 = new OracleConnection("Data Source=orcl;User id=scott; Password=system;");//oracleconnection类隶属于命名空间system.data.oracleclient
            
           
            OracleCommand oc1 = new OracleCommand("select loc as newloc  from dept", con1);
            OracleDataAdapter da = new OracleDataAdapter(oc1);
            DataSet ds1 = new DataSet();
            oda.Fill(ds1);

            //dataGridView1.DataSource = ds1.Tables[0];

            ////统计出列表中记录条数 tables.rows.count
            //this.Text = ds1.Tables[0].Rows.Count.ToString();

            //for (int i=0; i < ds1.Tables[0].Rows.Count; i++)
            //{
            //    //向combox添加子项items.add,dataset.tables.rows[行索引][列名字],此列名字对应oraclecommand中sql的列名
            //    comboBox1.Items.Add(ds1.Tables[0].Rows[i]["newloc"]);
            //}

            //comboBox1.DataSource = ds1.Tables[0].Columns["newloc"];
            //combox绑定数据库表查询数据集不用定位到每个列，和操作datagridview一样，定位到tables即可
            comboBox1.DataSource = ds1.Tables[0];
            //displaymember是展现给客户看的
            comboBox1.DisplayMember = "居住地";
            //valuemember为真正数据库中的列（或者sql的列或别名)
            comboBox1.ValueMember = "newloc";
        }