comboBox数据重复和绑定数据库后再加一个选择

[hao_t1021]

我做了一个comboBox联动,现在通过第一个comboBox中的选项,第二个comboBox可以显示相对应的数据,可是再通过第一个comboBox选择的时候,第二个comboBox中的数据是上一次的加上这一次的,怎么可以去掉上一次的数据,每次都显示当前这回选择的?
还有我想在加载的时候出现==请选择==,可是也没显示?
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";
}
}

[q107770540]

  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.Item.Clear(); //先清空再绑定
  comboBox2.Item.Add(new ListItem("=请选择=","0"); 
  comboBox2.DataSource = dtUser;
  comboBox2.DisplayMember = "goodsBrand";
  }
  }

[daihua_1113]

帮顶！！！！！！！！！！！11

[xiao__hui]

comboBox2.Item.Clear(); //先清空再绑定

[zzyhuian06142]

DataTable dtUser = ds.Tables["goodsInfo1"];
comboBox2.Item.Clear(); //先清空再绑定


要加“清选择”的话
DataTable dtUser = ds.Tables["goodsInfo1"];
DataRow dr = dtUser.NewRow;
dr[0] = "请选择";
comboBox2.DataSource = dtUser;
comboBox2.DisplayMember = "goodsBrand";

[zzyhuian06142]

DataTable dtUser = ds.Tables["goodsInfo1"];
comboBox2.Item.Clear(); //先清空再绑定


要加“清选择”的话
DataTable dtUser = ds.Tables["goodsInfo1"];
DataRow dr = dtUser.NewRow;
dr[0] = "请选择";
dtUser.Rows.Add(dr);
comboBox2.DataSource = dtUser;
comboBox2.DisplayMember = "goodsBrand";

[hao_t1021]

我用的是.net2005
q107770540
===============
comboBox2.Item.Clear(); //先清空再绑定
comboBox2.Item.Add(new ListItem("=请选择=","0");
你这方法不行,清空代码提示:设置 DataSource 属性后无法修改项集合。
添加选择项就不让通过.

zzyhuian06142
===============
输入字符串的格式不正确。不能在 goodsID 列中存储 <请选择>。所需类型是 Int32。

[zzyhuian06142]

[Quote=引用 6 楼 hao_t1021 的回复:]
我用的是.net2005
q107770540
===============
comboBox2.Item.Clear(); //先清空再绑定
comboBox2.Item.Add(new ListItem("=请选择=","0");
你这方法不行,清空代码提示:设置 DataSource 属性后无法修改项集合。
添加选择项就不让通过.

zzyhuian06142
==……
[/Quote]

我只是给你测试代码哦

DataTable dtUser = ds.Tables["goodsInfo1"];
comboBox2.Item.Clear(); //先清空再绑定


要加“清选择”的话
DataTable dtUser = ds.Tables["goodsInfo1"];
DataRow dr = dtUser.NewRow;
dr[0] = 0；加上这个
dr[1] = "请选择";
dtUser.Rows.Add(dr);
comboBox2.DataSource = dtUser;
comboBox2.DisplayMember = "goodsBrand";

[zzyhuian06142]

要自己会变通哦