将值从数据库插入到下拉列表失败

Question

我有州和城市下拉列表（级联），如下所示：

 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"));
}

我用来将值插入数据库，如下所示：

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

这可以正常工作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代码绑定状态但不绑定城市.city下拉列表仍显示--- Select ---。绑定城市后，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

Answer 1

尝试这个

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));

Answer 2

创建用于绑定cityDropdownlist的另一种方法：

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索引更改内部调用此方法：

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，然后分配值：

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()));