C# MVC4:Html.DropDownList是否未将值保存到模型实体？

我在MVC4应用程序中创建了一个

视图

，用于创建用户。在此视图中，用户可以为

组织

或

赞助商

设置属性，但不能同时为两者设置属性。我的当前代码根据开关选择显示的内容正确显示所有组织/赞助商，但当我在

DropDownList

中进行选择并保存新用户时，所有DropDownLists返回的

Null

值都是

用户的
值

用户模型（部分）：

    [GridColumn(Title = "Org.", SortEnabled = true, Width = "100")]
    public int? MemberOrgId { get; set; }

    [NotMappedColumn]
    public int? SponsorOrgId { get; set; }

    [ForeignKey("MemberOrgId")]
    [NotMappedColumn]
    public virtual MemberOrganizations Organization { get; set; }

    [ForeignKey("SponsorOrgId")]
    [NotMappedColumn]
    public virtual SponsorOrganizations Sponsor { get; set; }

@model PROJECT.Models.Users

@{
    ViewBag.Title = "Create";
    Layout = "~/Areas/Admin/.../.../.../_AdminLayout.cshtml";
    string cancelEditUrl = "/Admin/UserController/";
}

@using (Html.BeginForm("Create", "UserController", FormMethod.Post, new { enctype = "multipart/form-data" })) {
    @Html.AntiForgeryToken()
    @Html.ValidationSummary(true)

    @Html.HiddenFor(model => model.RegisteredDate)

    <div class="container">
        <div class="row">
            <div class="editor-label">
                @Html.LabelFor(model => model.Email)
            </div>
            <div class="editor-field" style="margin-bottom: 15px">
                @Html.TextBoxFor(model => model.Email, new { @class = "form-control" })
                @Html.ValidationMessageFor(model => model.Email)
            </div>
        </div>

        <input type="checkbox" value="12345" name="Sponsor-Organization" checked class="userCreate-BSSwitch"/> 

        <div style="margin-bottom: 15px">        
            <div class="row switchOn">
                <div class="editor-label">
                    @Html.LabelFor(model => model.MemberOrgId, "Organization")
                </div>
                <div class="editor-field">
                    @Html.DropDownList("OrganizationId", null, String.Empty, new { @class = "form-control", @id = "OrgIdDropDown" })
                    @Html.ValidationMessageFor(model => model.MemberOrgId)
                </div>
            </div>

            <div class="row switchOff">
                <dliv class="editor-label">
                    @Html.LabelFor(model => model.SponsorOrgId, "Sponsor")
                </dliv>
                <div class="editor-field" >
                    @Html.DropDownList("SponsorId", null, String.Empty, new { @class = "form-control", @id = "SponsorIdDropDown" })
                    @Html.ValidationMessageFor(model => model.SponsorOrgId)
                </div>
            </div>
        </div>

        <div class="row" id="submitRow">
            <div class="btn-group ">
                <button type="submit" value="Save" class="btn btn-success">Create User</button>
            </div>
            <a href="@cancelEditUrl" onclick="confirmCancel()" class="btn btn-danger">Cancel</a>

        </div>
    </div>
}

@section Scripts {
    @Scripts.Render("~/bundles/jqueryval")
}

<script type="text/javascript">
    jQuery(document).ready(function () {
        setTimeout(function () { $("#alert").alert('close'); }, 5000);
        $('.switchOff').addClass('hide');

    });  
    $.fn.bootstrapSwitch.defaults.onText = 'Member';
    $.fn.bootstrapSwitch.defaults.offText = 'Sponsor';
    $.fn.bootstrapSwitch.defaults.offColor = 'info';
    $.fn.bootstrapSwitch.defaults.animate = false;

    //$.fn.bootstrapSwitch.defaults.size = 'large';
    $(document).ready(function () {
        $('input:checkbox[name="Sponsor-Organization"]').bootstrapSwitch();
    });

    $('input:checkbox[name="Sponsor-Organization"]').on('switchChange.bootstrapSwitch', function (event, state) {
        var checked = state;
        if (checked) {
            $('.switchOn').removeClass('hide');
            $('.switchOff').addClass('hide');
            $('#SponsorIdDropDown').val("");
        }
        else {
            $('.switchOff').removeClass('hide');
            $('.switchOn').addClass('hide');
            $('#OrgIdDropDown').val("");
        }
    });

    $(document).ready(function () {
        $(".btn-danger").click(function () {
            var cancel = confirm("Are you sure? Entered data will be lost.")
            if (cancel != true) {
                event.preventDefault(); // cancel the event
            }
        });
    });

    //$('input:checkbox[name="Sponsor-Organization"]').on('switchChange.bootstrapSwitch', function(event, state) {
</script>

//
        // GET: /Admin/
        public ActionResult Create()
        {
            ViewBag.headerTitle = "Create a User";

            ViewBag.OrganizationId = new SelectList(db.MemberOrganizations, "Id", "Name");
            ViewBag.SponsorId = new SelectList(db.SponsorOrganizations, "Id", "Name");
            Users newUser = new Users();
            newUser.RegisteredDate = DateTime.Now;
            newUser.LastVisitDate = DateTime.Now;
            newUser.ProfilePictureSrc = null;
            return View(newUser);
        }

    [HttpPost]
    [ValidateAntiForgeryToken]
    public ActionResult Create(Users users)
    {
        ViewBag.headerTitle = "Create a User";

        if (ModelState.IsValid)
        {
            WebSecurity.CreateUserAndAccount(users.Email, "defaultPassword");

            Users user2 = db.Users.Where(u => u.Email == users.Email).FirstOrDefault();

            user2.Enabled = true;
            user2.Password = Membership.GeneratePassword(15, 7);
            user2.ForumUsername = users.Name;
            user2.RegisteredDate = DateTime.Now;
            user2.ReceiveSystemEmails = true;
            db.Entry(user2).State = EntityState.Modified;
            db.SaveChanges();

            string[] roleNames = new string[] { "role1", "role2", "role3" };
            System.Web.Security.Roles.AddUserToRoles(users.Email, roleNames);

            return RedirectToAction("Index");
        }
    }

创建（视图）：

    [GridColumn(Title = "Org.", SortEnabled = true, Width = "100")]
    public int? MemberOrgId { get; set; }

    [NotMappedColumn]
    public int? SponsorOrgId { get; set; }

    [ForeignKey("MemberOrgId")]
    [NotMappedColumn]
    public virtual MemberOrganizations Organization { get; set; }

    [ForeignKey("SponsorOrgId")]
    [NotMappedColumn]
    public virtual SponsorOrganizations Sponsor { get; set; }

@model PROJECT.Models.Users

@{
    ViewBag.Title = "Create";
    Layout = "~/Areas/Admin/.../.../.../_AdminLayout.cshtml";
    string cancelEditUrl = "/Admin/UserController/";
}

@using (Html.BeginForm("Create", "UserController", FormMethod.Post, new { enctype = "multipart/form-data" })) {
    @Html.AntiForgeryToken()
    @Html.ValidationSummary(true)

    @Html.HiddenFor(model => model.RegisteredDate)

    <div class="container">
        <div class="row">
            <div class="editor-label">
                @Html.LabelFor(model => model.Email)
            </div>
            <div class="editor-field" style="margin-bottom: 15px">
                @Html.TextBoxFor(model => model.Email, new { @class = "form-control" })
                @Html.ValidationMessageFor(model => model.Email)
            </div>
        </div>

        <input type="checkbox" value="12345" name="Sponsor-Organization" checked class="userCreate-BSSwitch"/> 

        <div style="margin-bottom: 15px">        
            <div class="row switchOn">
                <div class="editor-label">
                    @Html.LabelFor(model => model.MemberOrgId, "Organization")
                </div>
                <div class="editor-field">
                    @Html.DropDownList("OrganizationId", null, String.Empty, new { @class = "form-control", @id = "OrgIdDropDown" })
                    @Html.ValidationMessageFor(model => model.MemberOrgId)
                </div>
            </div>

            <div class="row switchOff">
                <dliv class="editor-label">
                    @Html.LabelFor(model => model.SponsorOrgId, "Sponsor")
                </dliv>
                <div class="editor-field" >
                    @Html.DropDownList("SponsorId", null, String.Empty, new { @class = "form-control", @id = "SponsorIdDropDown" })
                    @Html.ValidationMessageFor(model => model.SponsorOrgId)
                </div>
            </div>
        </div>

        <div class="row" id="submitRow">
            <div class="btn-group ">
                <button type="submit" value="Save" class="btn btn-success">Create User</button>
            </div>
            <a href="@cancelEditUrl" onclick="confirmCancel()" class="btn btn-danger">Cancel</a>

        </div>
    </div>
}

@section Scripts {
    @Scripts.Render("~/bundles/jqueryval")
}

<script type="text/javascript">
    jQuery(document).ready(function () {
        setTimeout(function () { $("#alert").alert('close'); }, 5000);
        $('.switchOff').addClass('hide');

    });  
    $.fn.bootstrapSwitch.defaults.onText = 'Member';
    $.fn.bootstrapSwitch.defaults.offText = 'Sponsor';
    $.fn.bootstrapSwitch.defaults.offColor = 'info';
    $.fn.bootstrapSwitch.defaults.animate = false;

    //$.fn.bootstrapSwitch.defaults.size = 'large';
    $(document).ready(function () {
        $('input:checkbox[name="Sponsor-Organization"]').bootstrapSwitch();
    });

    $('input:checkbox[name="Sponsor-Organization"]').on('switchChange.bootstrapSwitch', function (event, state) {
        var checked = state;
        if (checked) {
            $('.switchOn').removeClass('hide');
            $('.switchOff').addClass('hide');
            $('#SponsorIdDropDown').val("");
        }
        else {
            $('.switchOff').removeClass('hide');
            $('.switchOn').addClass('hide');
            $('#OrgIdDropDown').val("");
        }
    });

    $(document).ready(function () {
        $(".btn-danger").click(function () {
            var cancel = confirm("Are you sure? Entered data will be lost.")
            if (cancel != true) {
                event.preventDefault(); // cancel the event
            }
        });
    });

    //$('input:checkbox[name="Sponsor-Organization"]').on('switchChange.bootstrapSwitch', function(event, state) {
</script>

//
        // GET: /Admin/
        public ActionResult Create()
        {
            ViewBag.headerTitle = "Create a User";

            ViewBag.OrganizationId = new SelectList(db.MemberOrganizations, "Id", "Name");
            ViewBag.SponsorId = new SelectList(db.SponsorOrganizations, "Id", "Name");
            Users newUser = new Users();
            newUser.RegisteredDate = DateTime.Now;
            newUser.LastVisitDate = DateTime.Now;
            newUser.ProfilePictureSrc = null;
            return View(newUser);
        }

    [HttpPost]
    [ValidateAntiForgeryToken]
    public ActionResult Create(Users users)
    {
        ViewBag.headerTitle = "Create a User";

        if (ModelState.IsValid)
        {
            WebSecurity.CreateUserAndAccount(users.Email, "defaultPassword");

            Users user2 = db.Users.Where(u => u.Email == users.Email).FirstOrDefault();

            user2.Enabled = true;
            user2.Password = Membership.GeneratePassword(15, 7);
            user2.ForumUsername = users.Name;
            user2.RegisteredDate = DateTime.Now;
            user2.ReceiveSystemEmails = true;
            db.Entry(user2).State = EntityState.Modified;
            db.SaveChanges();

            string[] roleNames = new string[] { "role1", "role2", "role3" };
            System.Web.Security.Roles.AddUserToRoles(users.Email, roleNames);

            return RedirectToAction("Index");
        }
    }

控制器（创建HTTP Post）：

    [GridColumn(Title = "Org.", SortEnabled = true, Width = "100")]
    public int? MemberOrgId { get; set; }

    [NotMappedColumn]
    public int? SponsorOrgId { get; set; }

    [ForeignKey("MemberOrgId")]
    [NotMappedColumn]
    public virtual MemberOrganizations Organization { get; set; }

    [ForeignKey("SponsorOrgId")]
    [NotMappedColumn]
    public virtual SponsorOrganizations Sponsor { get; set; }

@model PROJECT.Models.Users

@{
    ViewBag.Title = "Create";
    Layout = "~/Areas/Admin/.../.../.../_AdminLayout.cshtml";
    string cancelEditUrl = "/Admin/UserController/";
}

@using (Html.BeginForm("Create", "UserController", FormMethod.Post, new { enctype = "multipart/form-data" })) {
    @Html.AntiForgeryToken()
    @Html.ValidationSummary(true)

    @Html.HiddenFor(model => model.RegisteredDate)

    <div class="container">
        <div class="row">
            <div class="editor-label">
                @Html.LabelFor(model => model.Email)
            </div>
            <div class="editor-field" style="margin-bottom: 15px">
                @Html.TextBoxFor(model => model.Email, new { @class = "form-control" })
                @Html.ValidationMessageFor(model => model.Email)
            </div>
        </div>

        <input type="checkbox" value="12345" name="Sponsor-Organization" checked class="userCreate-BSSwitch"/> 

        <div style="margin-bottom: 15px">        
            <div class="row switchOn">
                <div class="editor-label">
                    @Html.LabelFor(model => model.MemberOrgId, "Organization")
                </div>
                <div class="editor-field">
                    @Html.DropDownList("OrganizationId", null, String.Empty, new { @class = "form-control", @id = "OrgIdDropDown" })
                    @Html.ValidationMessageFor(model => model.MemberOrgId)
                </div>
            </div>

            <div class="row switchOff">
                <dliv class="editor-label">
                    @Html.LabelFor(model => model.SponsorOrgId, "Sponsor")
                </dliv>
                <div class="editor-field" >
                    @Html.DropDownList("SponsorId", null, String.Empty, new { @class = "form-control", @id = "SponsorIdDropDown" })
                    @Html.ValidationMessageFor(model => model.SponsorOrgId)
                </div>
            </div>
        </div>

        <div class="row" id="submitRow">
            <div class="btn-group ">
                <button type="submit" value="Save" class="btn btn-success">Create User</button>
            </div>
            <a href="@cancelEditUrl" onclick="confirmCancel()" class="btn btn-danger">Cancel</a>

        </div>
    </div>
}

@section Scripts {
    @Scripts.Render("~/bundles/jqueryval")
}

<script type="text/javascript">
    jQuery(document).ready(function () {
        setTimeout(function () { $("#alert").alert('close'); }, 5000);
        $('.switchOff').addClass('hide');

    });  
    $.fn.bootstrapSwitch.defaults.onText = 'Member';
    $.fn.bootstrapSwitch.defaults.offText = 'Sponsor';
    $.fn.bootstrapSwitch.defaults.offColor = 'info';
    $.fn.bootstrapSwitch.defaults.animate = false;

    //$.fn.bootstrapSwitch.defaults.size = 'large';
    $(document).ready(function () {
        $('input:checkbox[name="Sponsor-Organization"]').bootstrapSwitch();
    });

    $('input:checkbox[name="Sponsor-Organization"]').on('switchChange.bootstrapSwitch', function (event, state) {
        var checked = state;
        if (checked) {
            $('.switchOn').removeClass('hide');
            $('.switchOff').addClass('hide');
            $('#SponsorIdDropDown').val("");
        }
        else {
            $('.switchOff').removeClass('hide');
            $('.switchOn').addClass('hide');
            $('#OrgIdDropDown').val("");
        }
    });

    $(document).ready(function () {
        $(".btn-danger").click(function () {
            var cancel = confirm("Are you sure? Entered data will be lost.")
            if (cancel != true) {
                event.preventDefault(); // cancel the event
            }
        });
    });

    //$('input:checkbox[name="Sponsor-Organization"]').on('switchChange.bootstrapSwitch', function(event, state) {
</script>

//
        // GET: /Admin/
        public ActionResult Create()
        {
            ViewBag.headerTitle = "Create a User";

            ViewBag.OrganizationId = new SelectList(db.MemberOrganizations, "Id", "Name");
            ViewBag.SponsorId = new SelectList(db.SponsorOrganizations, "Id", "Name");
            Users newUser = new Users();
            newUser.RegisteredDate = DateTime.Now;
            newUser.LastVisitDate = DateTime.Now;
            newUser.ProfilePictureSrc = null;
            return View(newUser);
        }

    [HttpPost]
    [ValidateAntiForgeryToken]
    public ActionResult Create(Users users)
    {
        ViewBag.headerTitle = "Create a User";

        if (ModelState.IsValid)
        {
            WebSecurity.CreateUserAndAccount(users.Email, "defaultPassword");

            Users user2 = db.Users.Where(u => u.Email == users.Email).FirstOrDefault();

            user2.Enabled = true;
            user2.Password = Membership.GeneratePassword(15, 7);
            user2.ForumUsername = users.Name;
            user2.RegisteredDate = DateTime.Now;
            user2.ReceiveSystemEmails = true;
            db.Entry(user2).State = EntityState.Modified;
            db.SaveChanges();

            string[] roleNames = new string[] { "role1", "role2", "role3" };
            System.Web.Security.Roles.AddUserToRoles(users.Email, roleNames);

            return RedirectToAction("Index");
        }
    }

有人对这件事有什么想法吗？我试过在其他问题中找到的一些不同的建议，但到目前为止还没有任何效果。这是我的第一个MVC应用程序，所以我觉得我可能忽略了一些非常基本的东西。
对于要绑定到模型的字段，它必须位于“for”助手中（显示除外）。尝试像这样更改下拉列表

@Html.DropDownListFor(x => x.OrganizationId, null, String.Empty, new { @class = "form-control"})

@Html.DropDownListFor(x => x.SponsorId, null, String.Empty, new { @class = "form-control" })

假设您的用户模型具有字段OrganizationId和SponsorId，这些字段将绑定到下拉列表（在get上设置它们，下拉列表将被设置，下拉列表值将通过post传递回控制器）

编辑

我建议通过你的模型传递你的下拉列表。添加到您的模型中

public SelectList OrganizationList { get; set; }
public SelectList SponsorList { get; set; }

然后在控制器上（在get中）

那么在你看来

@Html.DropDownListFor(x => x.MemberOrgId, Model.OrganizationList, new { @class = "form-control" })

公共类MyModel
{
公共MyModel（）
{
this.myDDLList=新列表（）；
}   
公共列表myDDLList{get；set；}
公共int ddlID{get；set；}
} 
公共行动结果索引（）
{
MyModel model=新的MyModel（）；
使用（YourEntities上下文=新建YourEntities（））
{
var list=context.YourTable.ToList（）；
foreach（列表中的变量项）
{
model.myDDLList.Add（新的SelectListItem（）{Text=item.NameField，Value=item.ValueField.ToString（）}）；
}              
}
返回视图（模型）；
}
@DropDownListFor（x=>x.ddlID，Model.myDDLList）
我通过使用
ViewData[]
将预先填充的选择列表从我的控制器传递到我的视图，解决了这个问题：

    // GET: /Admin/
    public ActionResult Create()
    {
        ViewBag.headerTitle = "Create a User";
        ViewData["Organization"] = new SelectList(db.MemberOrganizations, "Id", "Name");
        ViewData["Sponsor"] = new SelectList(db.SponsorOrganizations, "Id", "Name");
        Users newUser = new Users();
        newUser.RegisteredDate = DateTime.Now;
        newUser.LastVisitDate = DateTime.Now;
        newUser.ProfilePictureSrc = null;
        return View(newUser);
    }

然后在我的视图中，只需将
ViewData[]
值读入我的
Html.DropDownList
，作为单独的
SelectList
：

@Html.DropDownList("MemberOrgId", ViewData["Organization"] as SelectList, String.Empty, new { @class = "form-control", @id = "MemberOrgId" })
@Html.DropDownList("SponsorOrgId", ViewData["Sponsor"] as SelectList, String.Empty, new { @class = "form-control", @id = "SponsorOrgId" })

当您说“所有DropDownLists返回的对于用户是空值”时，您的意思是控制器中的用户的属性是空的？您的模型中是否有名为OrganizationId和SponsorId的属性？因为这是视图中绑定下拉列表选择的地方。当我的控制器Create（）方法的HTTP Post完成时，如果我在下拉列表中选择了一个值，则会创建用户，但相应的字段仍然指定为
NULL
。我忘了在我的模型中将
OrganizationId
更改为
MemberOrgID
，
SponsorId
更改为
sponsorgid
。我原以为将
@Html.DropDownList（）
更改为引用那些可以修复它，但现在我收到：
@Html.DropDownList（“MemberOrgId”，null，String.Empty，new{@class=“form control”，@id=“OrgIdDropDown”}）
-
没有类型为“IEnumerable”的ViewData项具有键“MemberOrgId”
我在上面列出了相关的
用户
模型字段。我尝试了
@Html.DropDownListFor（x=>x.MemberOrgId，null，string.Empty，new{@class=“form control”，@id=“OrgIdDropDown”}）
，但我的视图无法加载：，
没有“IEnumerable”类型的ViewData项具有“MemberOrgId”键。
？我添加了一个关于如何通过模型而不是视图数据/包传递下拉列表的编辑。尝试新代码我不确定如何在MVC中查询数据库中的列表？我在控制器中为我的Create（）添加了GET。我更改了编辑以使用您的代码。由于您有2个下拉列表，因此您的模型中应该有2个“选定”字段。在我的示例中，下拉列表的选定值将传回MemberOrgId字段中的控制器。我不知道这是否是您希望所选值进入的字段，也不确定您希望另一个下拉列表进入的字段。为了安全起见，我清除了数据库和迁移，并执行了新的InitialCreate。我更新了数据库，然后添加了您在编辑中指定的所有内容。但是，当我现在尝试运行时，我在HomeController上遇到一个内部异常：
从第6行开始映射片段时出现问题：没有为Set Users中的properties Users.OrganizationList、Users.SponsorList指定映射。\r\n当：\r\n Entity为type[PROJECT.DAL.Users]
时，具有键（PK）的实体将不会往返？