comboBox的三级联动问题

Question

为什么comboBox2和comboBox3里面都会有上一次留下的内容呢,请问怎么取消,还有我想在加载的时候显示==请选择==
private void dataExcel_Load(object sender, EventArgs e)
        {
            db.RunSQL("select goodsoffer from goodsInfo group by goodsoffer", ref ds, "goodsInfo");
            
            DataTable dtGroup = ds.Tables["goodsInfo"];
            comboBox1.DataSource = dtGroup;
            comboBox1.DisplayMember = "goodsOffer";
            
        }        private void comboBox1_SelectedIndexChanged(object sender, EventArgs e)
        {
            if (comboBox1.SelectedIndex > -1)
            {
                DataRowView drv = (DataRowView)comboBox1.SelectedItem;
                string gId = drv.Row["goodsOffer"].ToString();
                db.RunSQL("select goodsID,goodsBrand from goodsInfo where goodsoffer='" + gId + "'", ref ds, "goodsInfo1");                DataTable dtUser = ds.Tables["goodsInfo1"];
                comboBox2.DataSource = dtUser;
                comboBox2.DisplayMember = "goodsBrand";
            }
        }

Answer 1

赋值之前 先清空之前的数据源comboBox1.DataSource = null;然后绑定

Answer 2

comboBox1.Items.Insert(0, new ListItem("==请选择==", "==请选择=="));

Answer 3

请问kevin_cheung在哪里做清空,是在绑定事件里吗,不好用

Answer 4

  private void comboBox1_SelectedIndexChanged(object sender, EventArgs e)
        {
            comboBox2.Items.Clear();
            if (comboBox1.SelectedIndex > -1)
            {
                DataRowView drv = (DataRowView)comboBox1.SelectedItem;
                string gId = drv.Row["goodsOffer"].ToString();
                db.RunSQL("select goodsID,goodsBrand from goodsInfo where goodsoffer='" + gId + "'", ref ds, "goodsInfo1");                DataTable dtUser = ds.Tables["goodsInfo1"];
                comboBox2.DataSource = dtUser;
                comboBox2.DisplayMember = "goodsBrand";
                comboBox2.Items.Insert(0,"==请选择==" )            }
        }

Answer 5

Zhanlixin
===================
按照你的方法做后,提示:设置DataSource属性后无法修改项集合

Answer 6

private void comboBox1_SelectedIndexChanged(object sender, EventArgs e)
        {
            //在这里清空
            if (comboBox1.SelectedIndex > -1)

Answer 7

在绑定数据时ComboBox1.Items.Clear()；
ComboBox1.Items.Insert(0, new ListItem("", "")); 

Answer 8

comboBox2.Items.Clear();后再绑定。