將值從數據庫插入到下拉列表失敗

Question

我有州和城市下拉列表（級聯），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"));
}

我用來將值插入數據庫，如下所示：

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

這可以正常工作並將州和城市插入數據庫表中。現在，我嘗試在編輯頁面上顯示如下值：

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

abpve代碼綁定狀態但不綁定城市.city下拉列表仍顯示--- Select ---。綁定城市后，我應該能夠選擇任何其他城市/州並再次更新。 任何幫助將不勝感激

Answer 1

嘗試這個

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

然后將城市值設置為隱藏值hf_city

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

然后關閉您的閱讀器和連接，然后再次調用在ddlState_SelectedIndexChanged上創建的函數

 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

創建用於綁定cityDropdownlist的另一種方法：

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索引更改內部調用此方法：

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

現在在編輯部分綁定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()));