根據MVC 4中的另一個下拉列表選擇值填充下拉列表

Question

我已經提到了 stackoverflow 這個 ans它工作正常但是因為我在表單中使用了下拉列表，所以當第二個下拉列表填充第一個下拉列表中的選定值時，它會受到影響。 如何保持這個價值？

這是我的代碼。

看法

@{ 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;
    }

並且當我只使用兩個下拉列表，即ddlCountry和ddlState並從ddlCountry選擇國家時，我的ddlSates得到了正確填充，但從ddlCountry選擇的國家正在發生變化。

Answer 1

這樣做了，而且效果很好

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);
    }

看法

@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);
        });
    });
});

Answer 2

你可以像下面這樣使用jquery

$("#select1").change(function() {
if ($(this).data('options') === undefined) {
/*Taking an array of all options-2 and kind of embedding it on the select1*/
$(this).data('options', $('#select2 option').clone());
}
var id = $(this).val();
var options = $(this).data('options').filter('[value=' + id + ']');
$('#select2').html(options);
});

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.0.0/jquery.min.js"></script>
<select name="select1" id="select1">
<option value="1">Fruit</option>
<option value="2">Animal</option>
<option value="3">Bird</option>
<option value="4">Car</option>
</select>


<select name="select2" id="select2">
<option value="1">Banana</option>
<option value="1">Apple</option>
<option value="1">Orange</option>
<option value="2">Wolf</option>
<option value="2">Fox</option>
<option value="2">Bear</option>
<option value="3">Eagle</option>
<option value="3">Hawk</option>
<option value="4">BWM<option>
</select>

Answer 3

                  <div class="col-md-4">
                    <div class="form-group">
                        <label for="validationCustom04">
                  @Html.LabelFor(model => model.LGAID)</label>
                       <select id="LocalID" name="LocalID" 
                     class="form-control" 
                  data-val="true" 
               data-val-number="Select Local Government">
                           <option value="0">---Select--</option>
                       </select>
                        <div class="invalid-feedback">
                            @Html.ValidationMessageFor(model => model.LGAID, "", new { @class = "text text-danger" })
                        </div>
                    </div>
                </div>

Answer 4

                  $("#State").change(function() {
               var Id = $("#localID option:Selected").val();
             $.getJSON('/ControllerName/ActionName/' + Id, 
           function (data) {
           var AddItem = '<option value="">---select from list--</option>';
        $.each(data, function (i, local) {
            AddItem += "<option value='" + local.LGAID + "'>" + local.LGAName + " 
            </option>"
        });

        $('#LocalID').html(AddItem);
           });
        });

Answer 5

[Route("PersonalData/localGoverntment")]
public ActionResult ActionName(int Id)
{
    DBEntities db = new DBEntities();

    List<LGA> LocalList = db.LGAs.ToList();
    List<LocalGModel> localModel = LocalList.Where(x => x.StateID == Id).Select(x => new LocalGModel { LGAID = x.LGAID, LGAName = x.LGAName }).ToList();

    return Json(localModel, JsonRequestBehavior.AllowGet);
}