Question

我有这个表名Item，当我编辑表的一行时，它返回State和City下拉列表的空值。但是在数据库中已经添加了但是dropdownlist显示为空我不知道如何检索选定的值在这里我使用的所有代码

此处为表项目

[Table("Item")]
public class Item
{
    [Key]
    [DatabaseGenerated(DatabaseGeneratedOption.Identity)]
    public int id { get; set; }
    [Required]
    public string name { get; set; }
    public string info { get; set; }
    public decimal price { get; set; }

    public int CatId { get; set; }

    public int? CountryId { get; set; }

    public int? StateId { get; set; }

    public int? CityId { get; set; }

    [ForeignKey("CatId")]
    public virtual Category Category { get; set; }

    [ForeignKey("CountryId")]
    public virtual Country Country { get; set; }

    [ForeignKey("StateId")]
    public virtual States States { get; set; }

    [ForeignKey("CityId")]
    public virtual City City { get; set; }

}

代码在项目控制器上编辑

 [HttpGet]
    public ActionResult Edite(int id)
    {

        List<Country> countrylist = db.CountryTb.ToList();
        SelectList s2 = new SelectList(countrylist.AsEnumerable(), "id", "name");
        ViewBag.SelectCountry = s2;


        Item I = db.Items.Single(x => x.id == id);

        return View(I);
    }


    [HttpPost]
    [ActionName("Edite")]
    public ActionResult Edite_post(int id)
    {
        Item I = db.Items.Single(x => x.id == id);
        UpdateModel(I, null, null, new string[] { "id" });
        db.SaveChanges();
        return RedirectToAction("Index");
    }

这是我的jQuery代码，但我认为它只在onchange上工作我希望它也可以工作onload来检索选定的值

<script>
    $(function () {
        $("#CountryId").change(function () {
            $.get("/Country/GetStatesById", { ID: $("#CountryId").val() }, function (data) {
                $("#StateId").empty();
                $.each(data, function (index, row) {
                    $("#StateId").append(" <option value='" + row.state_id + "'>" + row.name + "</option>")
                });
            })
        });
    });

</script>

<script>
    $(function () {
        $("#StateId").change(function () {
            $.get("/Country/GetCitiesById", { ID: $("#StateId").val() }, function (data) {
                $("#CityId").empty();
                $.each(data, function (index, row) {
                    $("#CityId").append(" <option value='" + row.id + "'>" + row.name + "</option>")
                });
            })
        });
    });

</script>

这里是我的HTML代码

 <!--Country-->
        <div class="form-group">
            @Html.LabelFor(model => model.CountryId, htmlAttributes: new { @class = "control-label col-md-2" })
            <div class="col-md-10">
                @Html.DropDownList("CountryId", (SelectList)ViewBag.SelectCountry, "select please", new { @class = "form-control" })
                @Html.ValidationMessageFor(model => model.CountryId, "", new { @class = "text-danger" })
            </div>
        </div>

        <!--States-->
        <div class="form-group">
            @Html.LabelFor(model => model.StateId, htmlAttributes: new { @class = "control-label col-md-2" })
            <div class="col-md-10">
                @Html.DropDownList("StateId", new SelectList(Enumerable.Empty<SelectListItem>(), "state_id", "name"), "-- Select --", new { @class = "form-control" })
                @Html.ValidationMessageFor(model => model.StateId, "", new { @class = "text-danger" })
            </div>
        </div>

        <!--City-->
        <div class="form-group">
            @Html.LabelFor(model => model.CityId, htmlAttributes: new { @class = "control-label col-md-2" })
            <div class="col-md-10">
                @Html.DropDownList("CityId", new SelectList(Enumerable.Empty<SelectListItem>(), "id", "name"), "-- Select --", new { @class = "form-control" })
                @Html.ValidationMessageFor(model => model.CityId, "", new { @class = "text-danger" })
            </div>
        </div>

此处表格类别

[Table("Category")]
public class Category
{
    [Key]
    [DatabaseGenerated(DatabaseGeneratedOption.Identity)]
    public int id { get; set; }

    [Required]
    public string name { get; set; }

    public virtual ICollection<Item> Items { get; set; }
}

此处为国家/地区

[Table("countries")]
public class Country
{
    [Key]
    [DatabaseGenerated(DatabaseGeneratedOption.Identity)]
    public int id { get; set; }

    public string sortname { get; set; }

    public string name { get; set; }

    public virtual ICollection<States> states { get; set; }

    public virtual ICollection<Item> Items { get; set; }
}

此处表格状态

[Table("states")]
public class States
{
    [Key]
    [DatabaseGenerated(DatabaseGeneratedOption.Identity)]
    public int state_id { get; set; }

    public string name { get; set; }

    public int country_id { get; set; }

    [ForeignKey("country_id")]
    public virtual Country countries { get; set; }

    public virtual ICollection<City> cities { get; set; }

    public virtual ICollection<Item> Items { get; set; }
}

这里是表城市

[Table("cities")]
public class City
{
    [Key]
    [DatabaseGenerated(DatabaseGeneratedOption.Identity)]
    public int id { get; set; }

    public string name { get; set; }

    public int state_id { get; set; }

    [ForeignKey("state_id")]
    public virtual States states { get; set; }
    public virtual ICollection<Item> Items { get; set; }
}

Answer 1

在@DropDownList上尝试更改@DropDownListFor(c => c.CountryID, (SelectList)ViewBag.SelectCountry, "select please", new { @class = "form-control" }) Begin窗体将显示更改值选项下拉列表，您的示例CountryID将发送给您的控制器

Answer 2

问题可能是因为您可能没有设置正确的导航属性。您提到 Foriegn键的方式有效，但缺少反向导航。请将以下行添加到相应的类中。

public virtual ICollection<Category> Categories { get; set; }

public virtual ICollection<Country> Countries { get; set; }

public virtual ICollection<States> States { get; set; }

public virtual ICollection<City> Cities { get; set; }

有关实体框架导航属性和关系

的更多information，请参阅此链接

当我点击编辑按钮时，MVC从数据库中检索选定的值到级联onload

2 个答案: