Question

DropDownList实现省级-市级-县-镇；联动

我在其中遇到了 无论如何后台获取到的值永远是第一个，我绑定数据的时候加了IsPostBack判断了的，求解。。。

Answer 1

你说的“无论什么时候后台获取到的值永远是第一个”是什么意思？感觉你表意太不明确了，是选择某项后，所选的值还是第一项还是怎么呢？如果是这种情况的话可能就是SelectedIndexChanged事件根本就没触发，这时你就得检查你的DropDownList是否加了AutoPostBack属性了，只有这个属性的值为True才能触发事件，这里和IsPostBack没多大关系的，IsPostBac只是判断是否是回发请求的.....

追问

都设定了的。。这个没错吧

追答

没错是得这样设定。但你刚才所说的获取到的值永远是第一个，是什么意思呢，你能具体描述下你的问题吗？不然这样我也说不清，我也不知道你的后台代码是怎样写的啊

追问

什么都没错，我重新建立一个页面之后 代码复制过去就对了。。奇葩啊。。你有没有用DropDownList实现 省 -市-县 绑定数据库三级联动的例子呢，有的话发下邮箱 787348086@qq.com谢谢哈！！

Answer 2

参考：
private void bind(){

SqlConnection conn = db.createConn();
string sqlRent = "select * from Rental";
conn.Open();
SqlCommand cmdRent = new SqlCommand(sqlRent, conn);
SqlDataReader sdrRent=cmdRent.ExecuteReader();
ddl_renting.DataSource = sdrRent;
ddl_renting.DataTextField = "rentalName";
ddl_renting.DataValueField = "rentalId";
ddl_renting.DataBind();
sdrRent.Close();
string sqlCity = "select * from Provience";
SqlCommand cmdCity=new SqlCommand(sqlCity,conn);
SqlDataReader sdrCity = cmdCity.ExecuteReader();
ddl_city.DataSource = sdrCity;
ddl_city.DataTextField = "provienceName";
ddl_city.DataValueField = "provienceId";
ddl_city.DataBind();
sdrCity.Close();
string sqlQuyu = "select * from City where c_id="+ddl_city.SelectedValue;
SqlCommand cmdQuyu = new SqlCommand(sqlQuyu,conn);
SqlDataReader sdrQuyu = cmdQuyu.ExecuteReader();
ddl_quyu.DataSource = sdrQuyu;
ddl_quyu.DataTextField = "cityName";
ddl_quyu.DataValueField = "cityId";
ddl_quyu.DataBind();
sdrQuyu.Close();
string sqlCom = "select * from Community where com_id="+ddl_quyu.SelectedValue;
SqlCommand cmdCom = new SqlCommand(sqlCom,conn);
SqlDataReader sdrCom = cmdCom.ExecuteReader();
ddl_xiaoqu.DataSource = sdrCom;
ddl_xiaoqu.DataTextField = "communityName";
ddl_xiaoqu.DataValueField = "communityId";
ddl_xiaoqu.DataBind();
sdrCom.Close();
conn.Close();
}

protected void ddl_city_SelectedIndexChanged(object sender, EventArgs e)
{
SqlConnection conn=db.createConn();
string c_id = ddl_city.SelectedValue;
string sql = "select * from City where c_id="+c_id;
conn.Open();
SqlCommand cmd = new SqlCommand(sql,conn);
SqlDataReader sdr = cmd.ExecuteReader();
ddl_quyu.DataSource = sdr;
ddl_quyu.DataTextField = "cityName";
ddl_quyu.DataValueField = "cityId";
ddl_quyu.DataBind();
sdr.Close();
conn.Close();
}
protected void ddl_quyu_SelectedIndexChanged(object sender, EventArgs e)
{
SqlConnection conn = db.createConn();
string c_id = ddl_quyu.SelectedValue;
string sql = "select * from Community where com_id="+c_id;
conn.Open();
SqlCommand cmd = new SqlCommand(sql,conn);
SqlDataReader sdr = cmd.ExecuteReader();
ddl_xiaoqu.DataSource = sdr;
ddl_xiaoqu.DataTextField = "communityName";
ddl_xiaoqu.DataValueField = "communityId";
ddl_xiaoqu.DataBind();
sdr.Close();
conn.Close();
}

Answer 3

你的取值代码是不是 有点问题呢? ,下面三种取值方法，建议首选第一种
DropDownList1.SelectedItem.Value;
DropDownList1.SelectedValue;
DropDownList1.Items[DropDownList1.SelectedItem].Value;

追问

不是取值问题，都没发现什么问题，重新新建一个页面代码复制过去就对了。。奇葩。你有没有用DropDownList实现 省 -市-县 绑定数据库三级联动的例子呢，有的话发下邮箱 787348086@qq.com谢谢哈！！

追答

手里面没有，但网上很多啊，你百度下吧