根据MVC 4中的另一个下拉列表选定值填充一个下拉列表 [英] Populate a drop down list based on another drop down list selected value in MVC 4

问题描述

我已推荐stackoverflow的ans 工作正常，但是由于我已采用表单的下拉列表，因此当填充第二个下拉列表时，第一个下拉列表中的选定值将生效.如何保持该价值?

I have referred This ans of stackoverflow It is working fine but since i have taken drop down list in forms so when second dropdown list gets populate selected value in first dropdown list is getting effected. How to maintain that value??

这是我的代码.

查看

@{ Html.BeginForm("Create", "User", FormMethod.Post, new { enctype = "multipart/form-data" }); }
@Html.DropDownList("country", ViewData["Id"] as List<SelectListItem>, new { onchange = "this.form.submit();" })
@{ Html.EndForm(); }


@{ Html.BeginForm("Create", "User", FormMethod.Post, new { enctype = "multipart/form-data" }); }
@Html.DropDownList("state", ViewData["Id1"] as List<SelectListItem>, new { onchange = "this.form.submit();" })
@{ Html.EndForm(); }


@{ Html.BeginForm("Create", "User", FormMethod.Post, new { enctype = "multipart/form-data" }); }
@Html.DropDownList("city", ViewData["Id2"] as List<SelectListItem>, new { onchange = "this.form.submit();" })
@{ Html.EndForm(); }

控制器

 public ActionResult Create()
    {
        FillCountry();
        FillState();
        FillCity();
        return View();
    }
    [HttpPost]
    public ActionResult Create(User ur)
    {
        string str = @"Data Source=DEV_3\SQLEXPRESS;Initial Catalog=DB_Naved_Test;Integrated Security=True";
        SqlConnection con = new SqlConnection(str);
        string query = "Insert into tblTest (Name,Email,MobileNo) values('" + ur.Name + "','" + ur.Email + "','" + ur.MobileNo + "')";
        con.Open();
        SqlCommand cmd = new SqlCommand(query, con);
        cmd.ExecuteNonQuery();
        con.Close();
        TempData["msg"] = "<script>alert('Inserted Successfully');</script>";
        ModelState.Clear();
        FillCountry();
        FillState();
        FillCity();
        return View();


    }
    public void FillCountry()
    {
        string str = @"Data Source=DEV_3\SQLEXPRESS;Initial Catalog=DB_Naved_Test;Integrated Security=True";
        SqlConnection con = new SqlConnection(str);
        string query = "select * from tblCountry ";
        SqlCommand cmd = new SqlCommand(query, con);
        con.Open();
        SqlDataReader rdr = cmd.ExecuteReader();
        List<SelectListItem> li = new List<SelectListItem>();
        li.Add(new SelectListItem { Text = "Select", Value = "0" });
        while (rdr.Read())
        {
            li.Add(new SelectListItem { Text = rdr[1].ToString(), Value = rdr[0].ToString() });
        }
       
        ViewData["Id"] = li;
        
    }
    public void FillState()
    {
        int id = Convert.ToInt16(Request["country"]);
        string str = @"Data Source=DEV_3\SQLEXPRESS;Initial Catalog=DB_Naved_Test;Integrated Security=True";
        SqlConnection con = new SqlConnection(str);
        string query = "select * from tblState where cid='" + id + "'";
        SqlCommand cmd = new SqlCommand(query, con);
        con.Open();
        SqlDataReader rdr = cmd.ExecuteReader();
        List<SelectListItem> li = new List<SelectListItem>();
        li.Add(new SelectListItem { Text = "Select", Value = "0" });
        while (rdr.Read())
        {
            li.Add(new SelectListItem { Text = rdr[1].ToString(), Value = rdr[0].ToString() });
        }
        ViewData["Id1"] = li;
    }
    public void FillCity()
    {
        int id = Convert.ToInt16(Request["state"]);
        string str = @"Data Source=DEV_3\SQLEXPRESS;Initial Catalog=DB_Naved_Test;Integrated Security=True";
        SqlConnection con = new SqlConnection(str);
        string query = "select * from tbl_cities where StateId='" + id + "'";
        SqlCommand cmd = new SqlCommand(query, con);
        con.Open();
        SqlDataReader rdr = cmd.ExecuteReader();
        List<SelectListItem> li = new List<SelectListItem>();
        li.Add(new SelectListItem { Text = "Select", Value = "0" });
        while (rdr.Read())
        {
            li.Add(new SelectListItem { Text = rdr[1].ToString(), Value = rdr[0].ToString() });
        }
        ViewData["Id2"] = li;
    }

，当我仅使用两个下拉列表时，即 ddlCountry 和 ddlState ，并从 ddlCountry 我的 ddlSates 中选择国家/地区">已正确填充，但从 ddlCountry 中选择的国家/地区已更改.

and also when I am using only two dropdownlist i.e ddlCountry and ddlState and select Country from ddlCountry my ddlSates is getting populated properly but the selected Country from ddlCountry is getting changed.

推荐答案

做到了这一点，并且效果很好

Did this and it working perfect

控制器

public ActionResult Index()
    {
        string str = @"Data Source=DEV_3\SQLEXPRESS;Initial Catalog=DB_Naved_Test;Integrated Security=True";
        SqlConnection con = new SqlConnection(str);
        string query = "select * from tbl_country ";
        SqlCommand cmd = new SqlCommand(query, con);
        con.Open();
        SqlDataReader rdr = cmd.ExecuteReader();
        List<SelectListItem> li = new List<SelectListItem>();
        while (rdr.Read())
        {
            li.Add(new SelectListItem { Text = rdr[1].ToString(), Value = rdr[0].ToString() });
        }
        ViewData["country"] = li;
        return View();
    }
    public JsonResult StateList(int Id)
    {
        string str = @"Data Source=DEV_3\SQLEXPRESS;Initial Catalog=DB_Naved_Test;Integrated Security=True";
        SqlConnection con = new SqlConnection(str);
        string query = "select * from tbl_states where cid='" + Id + "'";
        SqlCommand cmd = new SqlCommand(query, con);
        con.Open();
        SqlDataReader rdr = cmd.ExecuteReader();
        List<SelectListItem> li = new List<SelectListItem>();
        while (rdr.Read())
        {
            li.Add(new SelectListItem { Text = rdr[1].ToString(), Value = rdr[0].ToString() });
        }
        return Json(li, JsonRequestBehavior.AllowGet);
    }
    public JsonResult Citylist(int id)
    {
        string str = @"Data Source=DEV_3\SQLEXPRESS;Initial Catalog=DB_Naved_Test;Integrated Security=True";
        SqlConnection con = new SqlConnection(str);
        string query = "select * from tbl_cities where stateid='" + id + "'";
        SqlCommand cmd = new SqlCommand(query, con);
        con.Open();
        SqlDataReader rdr = cmd.ExecuteReader();
        List<SelectListItem> li = new List<SelectListItem>();
        while (rdr.Read())
        {
            li.Add(new SelectListItem { Text = rdr[1].ToString(), Value = rdr[0].ToString() });
        }
        return Json(li, JsonRequestBehavior.AllowGet);
    }

查看

@using (Html.BeginForm())
{ @Html.DropDownList("Country", ViewData["country"] as SelectList, "Select Country", new { id = "Country", style = "width: 150px;" })<br />
<select id="State" name="state" , style="width: 150px;"></select><br />
<select id="city" name="City" , style="width: 150px;"></select><br />
}
@Scripts.Render("~/bundles/jquery")
<script type="text/jscript">
$(function ()
{
    $('#Country').change(function ()
    {        
        $.getJSON('/Cascading/StateList/' + $('#Country').val(), function (data)
        {
            var items = '<option>Select State</option>';
            $.each(data, function (i, state)
            {
                items += "<option value='" + state.Value + "'>" + state.Text + "</option>";
            });
            $('#State').html(items);
        });
    });

    $('#State').change(function ()
    {
        $.getJSON('/Cascading/Citylist/' + $('#State').val(), function (data)
        {
            var items = '<option>Select City</option>';
            $.each(data, function (i, city)
            {
                items += "<option value='" + city.Value + "'>" + city.Text + "</option>";
            });
            $('#city').html(items);
        });
    });
});

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