未将null值传递给actionresult ASP.NET MVC实体框架

Question

所以我使用的是一个用户界面，用户应该能够在其中编辑和删除数据库中的数据。但是当我试图发布表单时，它不会保存更改。这里有一些代码：

型号：

namespace Aviato.Models
{
    using System;
    using System.ComponentModel.DataAnnotations;
    using System.ComponentModel.DataAnnotations.Schema;
    public partial class TimesheetEntry
    {
        [Key]
        [Column(Order = 0)]
        [DatabaseGenerated(DatabaseGeneratedOption.None)]
        public int UserId { get; set; }
        [Key]
        [Column(Order = 1)]
        [StringLength(50)]
        public string ProjectId { get; set; }
        [Key]
        [Column(Order = 2, TypeName = "date")]
        public DateTime EntryDate { get; set; }
        public decimal HoursWorked { get; set; }
        public virtual Project Project { get; set; }
        public virtual User User { get; set; }
    }
}

视图：

（索引）

@model IEnumerable<Aviato.Models.TimesheetEntry>
@{
    Layout = "~/Views/Shared/_Layout.cshtml";
}
<h1>Tidrapportering</h1>
<p>
    @Html.ActionLink("Skapa ny", "Create")
</p>
<table class="table">
    <tr>
        <th>
            @Html.DisplayNameFor(model => model.UserId)
        </th>
        <th>
            @Html.DisplayNameFor(model => model.Project.ProjectName)
        </th>
        <th>
            @Html.DisplayNameFor(model => model.EntryDate)
        </th>
        <th>
            @Html.DisplayNameFor(model => model.HoursWorked)
        </th>
        <th></th>
    </tr>
    @foreach (var item in Model) {
        <tr>
            <td>
                @Html.DisplayFor(modelItem => item.UserId)
            </td>
            <td>
                @Html.DisplayFor(modelItem => item.Project.ProjectName)
            </td>
            <td>
                @Html.DisplayFor(modelItem => item.EntryDate)
            </td>
            <td>
                @Html.DisplayFor(modelItem => item.HoursWorked)
            </td>
            <td>
                @Html.ActionLink("Redigera", "Edit", new { id=item.UserId, item.ProjectId, item.EntryDate }) |
                @Html.ActionLink("Ta bort", "Delete", new { id=item.UserId, item.ProjectId, item.EntryDate})
            </td>
        </tr>
    }
</table>
<div>
    @Html.ActionLink("Tillbaka", "Index", "User")
</div>

（编辑）

@model Aviato.Models.TimesheetEntry
@{
    Layout = "~/Views/Shared/_Layout.cshtml";
}
<h1>Redigera</h1>
@using (Html.BeginForm())
{
    @Html.AntiForgeryToken()
    <div class="form-horizontal">
        <hr />
        @Html.ValidationSummary(true)
        @Html.HiddenFor(model => model.UserId)
        @Html.HiddenFor(model => model.Project)
        @Html.HiddenFor(model => model.User)
        <div class="form-group">
            @Html.LabelFor(model => model.ProjectId, htmlAttributes: new { @class = "control-label col-md-2" })
            <div class="col-md-10">
                @Html.EditorFor(model => model.ProjectId, new { htmlAttributes = new { @class = "form-control" } })
                @Html.ValidationMessageFor(model => model.ProjectId)
            </div>
        </div>
        <div class="form-group">
            @Html.LabelFor(model => model.EntryDate, htmlAttributes: new { @class = "control-label col-md-2" })
            <div class="col-md-10">
                @Html.EditorFor(model => model.EntryDate, new { htmlAttributes = new { @class = "form-control" } })
                @Html.ValidationMessageFor(model => model.EntryDate)
            </div>
        </div>
        <div class="form-group">
            @Html.LabelFor(model => model.HoursWorked, htmlAttributes: new { @class = "control-label col-md-2" })
            <div class="col-md-10">
                @Html.EditorFor(model => model.HoursWorked, new { htmlAttributes = new { @class = "form-control" } })
                @Html.ValidationMessageFor(model => model.HoursWorked)
            </div>
        </div>
        <div class="form-group">
            <div class="col-md-offset-2 col-md-10">
                <input type="submit" value="Spara" class="btn btn-default" />
            </div>
        </div>
    </div>
}
<div>
    @Html.ActionLink("Tillbaka", "Index")
</div>

控制器：

public ActionResult Edit(int? id, string projectId, DateTime entryDate)
        {
            if (id == null)
            {
                return new HttpStatusCodeResult(HttpStatusCode.BadRequest);
            }
            var timesheetentry = _db.TimesheetEntries.Find(id, projectId, entryDate);
            if (timesheetentry == null)
            {
                return HttpNotFound();
            }
            ViewBag.ProjectId = new SelectList(_db.Projects, "ProjectId", "ProjectName", timesheetentry.ProjectId);
            ViewBag.UserId = new SelectList(_db.Users, "UserId", "SocialSecurityNumber", timesheetentry.UserId);
            return View(timesheetentry);
        }
        [HttpPost]
        public ActionResult Edit(TimesheetEntry timesheetentry)
        {
            if (ModelState.IsValid) // So here's where the breakpoint skips. I get User and Project to be null in timesheetentry!
            {
                _db.Entry(timesheetentry).State = EntityState.Modified;
                _db.SaveChanges();
                return RedirectToAction("Index");
            }
            ViewBag.ProjectId = new SelectList(_db.Projects, "ProjectId", "ProjectName", timesheetentry.ProjectId);
            ViewBag.UserId = new SelectList(_db.Users, "UserId", "SocialSecurityNumber", timesheetentry.UserId);
            return View(timesheetentry);
        }

数据库：

CREATE TABLE [dbo].[TimesheetEntries] (
    [UserId]      INT            NOT NULL,
    [ProjectId]   NVARCHAR (50)  NOT NULL,
    [EntryDate]   DATE           NOT NULL,
    [HoursWorked] DECIMAL (8, 1) CONSTRAINT [DF_TimesheetEntries_HoursWorked] DEFAULT ((0.0)) NOT NULL,
    CONSTRAINT [PK_TimesheetEntries] PRIMARY KEY CLUSTERED ([UserId] ASC, [ProjectId] ASC, [EntryDate] ASC),
    CONSTRAINT [FK_TimesheetEntries_Users] FOREIGN KEY ([UserId]) REFERENCES [dbo].[Users] ([UserId]),
    CONSTRAINT [FK_TimesheetEntries_Projects] FOREIGN KEY ([ProjectId]) REFERENCES [dbo].[Projects] ([ProjectId])
);

Answer 1

好的，所以我可以理解为什么会发生这种情况。在您的编辑页面中，您有以下行

    @Html.HiddenFor(model => model.Project)
    @Html.HiddenFor(model => model.User)

但这还不足以使它能够往返于与这些子对象相关的所有数据。如果您在HTML页面上查看源代码，您应该明白我的意思。隐藏的HTML字段无法处理复杂的对象。如果您真的想往返这些对象，那么您需要将它们的所有字段输出为隐藏字段，或者创建一个模板来执行此操作。或者简单地创建一个不包含子对象的视图模型。

Answer 2

TimesheetEntryModel=new TimesheetEntryModel（）；return（Model）；

你这样用吗？