c# - 如何在 Asp.Net C# 中填充相关下拉列表

Question

我想填充两个下拉列表，根据第一个下拉列表的选择，第二个下拉列表将被填充。

例子 ：

就像我有两个下拉列表，即1.ddlCountry和2.ddlState

Now when country is selected then depending on the selected Country the States related with that Country will get populated in the State dropdownlist. 我想通过使用 C# 编码语言在 Asp.Net 中重新加载整个页面来实现这一点。

我怎样才能达到同样的效果？

Dropdownlist正在通过执行查询从数据库中获取数据。

Answer 1

1. 您可以AJAX toolkit CascadingDropDown按照Naresh. 或者
2. 使用ajax 更新面板并保留所有Dropdowns内容。所以整个页面不会在更改下拉值时加载。

您没有将代码提供给进一步的解决方案。

Answer 2

protected void ddlCountry_SelectedIndexChanged(object sender, EventArgs e)
{
  FillStateByCountry();
}
protected void ddlState_SelectedIndexChanged(object sender, EventArgs e)
{
  FillLocationByCountryandState();
}

private void FillStateByCountry()
{
    DataSet dstFillState;
    int CountryId = Convert.ToInt32(ddlCountry.SelectedValue.ToString());
    dstFillState = Tbl_State.FillDDLState(CountryId);
    ddlState.DataSource = dstFillState;
    ddlState.DataTextField = "State";
    ddlState.DataValueField = "Id";
    ddlState.DataBind();
}

相似地FillLocationByCountryandState();

Answer 3

在表单中添加两个下拉列表并将其命名为cmbStates,cmbCities

当您从中选择州名时cmbStates(dropwdownlist)，cmbCities(dropdownlist)根据州名（cmbStates）生成城市

通过从数据库中获取数据

  private void Form1_Load(object sender, EventArgs e)
    {
        SqlConnection con = new SqlConnection("server=pbs-server;database=p2p;user id=shekar;password=sekhar@1346");
        SqlCommand cmd = new SqlCommand("select states from Country", con);
        DataSet ds = new DataSet();
        SqlDataAdapter da = new SqlDataAdapter(cmd);
        con.Open();
        da.Fill(ds, "Country");
        cmbStates.DataSource = ds.Tables[0];
        cmbStates.SelectedValue = 0;
        con.Close();

    }

    private void cmbStates_SelectedIndexChanged(object sender, EventArgs e)
    {
        SqlConnection con = new SqlConnection("server=xxxx;database=xxxx;user id=xxxxr;password=xxxxxx");
        SqlCommand cmd = new SqlCommand("select cities from States where cityname = 'cmbStates.SelectedItem.ToString()'", con);
        DataSet ds = new DataSet();
        SqlDataAdapter da = new SqlDataAdapter(cmd);
        con.Open();
        da.Fill(ds, "States");
        cmbCities.DataSource = ds.Tables[0];
        cmbCities.SelectedValue = 0;
        con.Close();           

    }

或者

手动添加项目

namespace DropDownlist
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        private void Form1_Load(object sender, EventArgs e)
        {
            cmbStates.Items.Add("Andhra Pradesh");
            cmbStates.Items.Add("Tamilnadu");
            cmbStates.Items.Add("Karnataka");
            cmbStates.SelectedValue = 0;
        }

        private void cmbStates_SelectedIndexChanged(object sender, EventArgs e)
        {

            if (cmbStates.SelectedItem.ToString() == "Andhra Pradesh")
            {
                cmbCities.Items.Clear();
                cmbCities.Items.Add("Hyderabad");
                cmbCities.Items.Add("Guntur");
                cmbCities.Items.Add("Vijayawada");
                cmbCities.SelectedValue = 0;

            }
            else if (cmbStates.SelectedItem.ToString() == "Tamilnadu")
            {
                cmbCities.Items.Clear();
                cmbCities.Items.Add("Chennai");
                cmbCities.Items.Add("Coimbatore");
                cmbCities.Items.Add("ooty");
                cmbCities.SelectedValue = 0;

            }
            else if (cmbStates.SelectedItem.ToString() == "Karnataka")
            {
                cmbCities.Items.Clear();
                cmbCities.Items.Add("Bangalore");
                cmbCities.Items.Add("Mangalore");
                cmbCities.SelectedValue = 0;

            }
            else
            {
                MessageBox.Show("Please Select any value");
            }
        }
    }
}