将值从数据库插入到下拉列表失败答案

【问题标题】：Inserting value from database to dropdownlist fails将值从数据库插入到下拉列表失败
【发布时间】：2015-10-08 05:39:52
【问题描述】：

我有如下的州和城市下拉列表（级联）：

 protected void BindStateDropDown()
{
    string CS = ConfigurationManager.ConnectionStrings["SportsActiveConnectionString"].ConnectionString;
    using (SqlConnection con = new SqlConnection(CS))
    {
        con.Open();
        SqlCommand cmd = new SqlCommand("select * from tblState", con);
        SqlDataAdapter da = new SqlDataAdapter(cmd);
        DataSet ds = new DataSet();
        da.Fill(ds);
        ddlState.DataSource = ds;
        ddlState.DataTextField = "StateName";
        ddlState.DataValueField = "StateId";
        ddlState.DataBind();
    }
    ddlState.Items.Insert(0, new ListItem("---Select---", "0"));
    ddlCity.Items.Insert(0, new ListItem("---Select---", "0"));
}


protected void ddlState_SelectedIndexChanged(object sender, EventArgs e)
{
    int StatId = Convert.ToInt32(ddlState.SelectedValue);
    string CS = ConfigurationManager.ConnectionStrings["SportsActiveConnectionString"].ConnectionString;
    using (SqlConnection con = new SqlConnection(CS))
    {
        con.Open();
        SqlCommand cmd = new SqlCommand("spCities", con);
        cmd.Parameters.AddWithValue("@StatId", StatId);
        cmd.CommandType = CommandType.StoredProcedure;
        SqlDataAdapter da = new SqlDataAdapter(cmd);
        DataSet ds = new DataSet();
        da.Fill(ds);
        ddlCity.DataSource = ds;
        ddlCity.DataTextField = "CityName";
        ddlCity.DataValueField = "CityId";
        ddlCity.DataBind();
    }
    ddlCity.Items.Insert(0, new ListItem("---Select---", "0"));
}

我用来向数据库插入值如下：

 cmd.Parameters.AddWithValue("@State", ddlState.SelectedItem.Text);
 cmd.Parameters.AddWithValue("@City", ddlCity.SelectedItem.Text);

这工作正常并将州和城市插入数据库表中。现在我尝试在编辑页面上显示如下值：

 ddlState.SelectedIndex = ddlState.Items.IndexOf(ddlState.Items.FindByText(rdr["State"].ToString()));
 ddlCity.SelectedIndex = ddlCity.Items.IndexOf(ddlCity.Items.FindByText(rdr["City"].ToString()));

abpve 代码绑定了州，但没有绑定城市。城市下拉菜单仍然显示---选择---。一旦绑定了城市，我应该能够选择任何其他城市/州并再次更新。任何帮助将不胜感激

【问题讨论】：

能否请您发布绑定组合框的代码
请先绑定两个组合框，然后设置选定的索引。
对 ddlcity 和 ddlstate 使用不同的数据集
你试过用这个dlState.SelectedValue = rdr["State"].ToString();
@Suprabhat - 不，它甚至不绑定状态

标签： c# asp.net sql-server cascadingdropdown

【解决方案1】：

试试这个

ddlState.SelectedIndex = ddlState.Items.IndexOf(ddlState.Items.FindByText(rdr["State"].ToString()));

然后将城市值设置为隐藏值 hf_city

hf_city.Value = rdr["City"].ToString();

然后关闭您的阅读器和连接，然后再次调用您在 ddlState_SelectedIndexChanged 上创建的函数

 int StatId = Convert.ToInt32(ddlState.SelectedValue);
    string CS = ConfigurationManager.ConnectionStrings["SportsActiveConnectionString"].ConnectionString;
    using (SqlConnection con = new SqlConnection(CS))
    {
        con.Open();
        SqlCommand cmd = new SqlCommand("spCities", con);
        cmd.Parameters.AddWithValue("@StatId", StatId);
        cmd.CommandType = CommandType.StoredProcedure;
        SqlDataAdapter da = new SqlDataAdapter(cmd);
        DataSet ds = new DataSet();
        da.Fill(ds);
        ddlCity.DataSource = ds;
        ddlCity.DataTextField = "CityName";
        ddlCity.DataValueField = "CityId";
        ddlCity.DataBind();
    }
    ddlCity.Items.Insert(0, new ListItem("---Select---", "0"));

 ddlCity.SelectedIndex = ddlCity.Items.IndexOf(ddlCity.Items.FindByText(hf_city.Value));

【讨论】：

【解决方案2】：

创建另一个绑定cityDropdownlist的方法：

protected void BindCityDropDown(int StatId)
{
    string CS = ConfigurationManager.ConnectionStrings["SportsActiveConnectionString"].ConnectionString;
    using (SqlConnection con = new SqlConnection(CS))
    {
        con.Open();
        SqlCommand cmd = new SqlCommand("spCities", con);
        cmd.Parameters.AddWithValue("@StatId", StatId);
        cmd.CommandType = CommandType.StoredProcedure;
        SqlDataAdapter da = new SqlDataAdapter(cmd);
        DataSet ds = new DataSet();
        da.Fill(ds);
        ddlCity.DataSource = ds;
        ddlCity.DataTextField = "CityName";
        ddlCity.DataValueField = "CityId";
        ddlCity.DataBind();
    }
    ddlCity.Items.Insert(0, new ListItem("---Select---", "0"));
}

在 dropdownlistselected 索引更改中调用这个：

protected void ddlState_SelectedIndexChanged(object sender, EventArgs e)
{
    int StatId = Convert.ToInt32(ddlState.SelectedValue);
    BindCityDropdown(StatId);
}

现在在编辑部分绑定 citydropdownlist 然后赋值：

ddlState.SelectedIndex = ddlState.Items.IndexOf(ddlState.Items.FindByText(rdr["State"].ToString()));
int StatId = Convert.ToInt32(ddlState.SelectedValue);
BindCityDropdown(StatId);
 ddlCity.SelectedIndex = ddlCity.Items.IndexOf(ddlCity.Items.FindByText(rdr["City"].ToString()));

【讨论】：