c# - ASP.Net MVC 创建注册错误

Question

我在我的应用程序中运行了这个东西。我有 3 个表，1 个主表和创建主表所需的 2 个其他表，主表依赖于 2 个表，它们与约束连接。我有主表:Word然后我有另外两个表:困难和类别。我创建了难度:简单，然后创建了类别:自然。所以现在，我可以用这 2 个属性创建尽可能多的单词，但它给了我一个错误。只有这样才能创造出一个词

Dificulty -> Category -> Word

或

Category -> Difficulty -> Word

.如果不走那条路，我就无法创造一个词，我也不知道为什么。这些值存储在一个数据库中，该数据库将在 2 个组合框中调用，1 个用于难度，另一个用于类别。如果我想创建一个词，我需要创建一个新类别和一个新难度，否则它将返回 null。

这是我的模型 View :

public partial class palavra
    {
        public int id_pal { get; set; }
        public Nullable<int> LETRAS { get; set; }
        public string PISTA { get; set; }
        public int id_cat { get; set; }
        public int id_dificuldade { get; set; }
        public string nomepalavra { get; set; }

        public virtual  categoria categoria { get; set; }
       public virtual dificuldade dificuldade { get; set; }
    }

这是我的 Controller :

public ActionResult Index()
        {
            var palavras = db.palavras.Include(p => p.categoria).Include(p => p.dificuldade);
           return View(palavras.ToList());
        }



        // GET: palavras/Create
        public ActionResult Create()
        {
            ViewBag.id_cat = new SelectList(db.categorias, "id_cat", "TIPO_CATEGORIA");
            ViewBag.id_dificuldade = new SelectList(db.dificuldades, "id_dificuldade", "TIPO_DIFICULDADE");
            return View();
        }

        // POST: palavras/Create
        // To protect from overposting attacks, please enable the specific properties you want to bind to, for 
        // more details see http://go.microsoft.com/fwlink/?LinkId=317598.
        [HttpPost]
        [ValidateAntiForgeryToken]
        public ActionResult Create([Bind(Include = "id_pal,LETRAS,PISTA,id_cat,id_dificuldade,nomepalavra")] palavra palavra)
        {
            if (ModelState.IsValid)
            {
                db.palavras.Add(palavra);
                db.SaveChanges();
                return RedirectToAction("Index");
            }

            ViewBag.id_cat = new SelectList(db.categorias, "id_cat", "TIPO_CATEGORIA", palavra.id_cat);
            ViewBag.id_dificuldade = new SelectList(db.dificuldades, "id_dificuldade", "TIPO_DIFICULDADE", palavra.id_dificuldade);
            return View(palavra);
        }

这是我的观点:

<p>
    @Html.ActionLink("Create New", "Create")
</p>
<table class="table">
    <tr>
        <th>
            @Html.DisplayNameFor(model => model.nomepalavra)
        </th>
        <th>
            @Html.DisplayNameFor(model => model.LETRAS)
        </th>
        <th>
            @Html.DisplayNameFor(model => model.PISTA)
        </th>
        <th>
            @Html.DisplayNameFor(model => model.categoria.TIPO_CATEGORIA)
        </th>
        <th>
            @Html.DisplayNameFor(model => model.dificuldade.TIPO_DIFICULDADE)
        </th>
        <th></th>
    </tr>

@foreach (var item in Model) {
    <tr>
        <td>
            @Html.DisplayFor(modelItem => item.nomepalavra)
        </td>
        <td>
            @Html.DisplayFor(modelItem => item.LETRAS)
        </td>
        <td>
            @Html.DisplayFor(modelItem => item.PISTA)
        </td>
        <td>
            @Html.DisplayFor(modelItem => item.categoria.TIPO_CATEGORIA)
        </td>
        <td>
            @Html.DisplayFor(modelItem => item.dificuldade.TIPO_DIFICULDADE)
        </td>
        <td>
            @Html.ActionLink("Edit", "Edit", new { id=item.id_pal }) |
            @Html.ActionLink("Details", "Details", new { id=item.id_pal }) |
            @Html.ActionLink("Delete", "Delete", new { id=item.id_pal })
        </td>
    </tr>
}

每当我运行代码插入时，我都会收到此错误:

An exception of type 'System.Data.Entity.Infrastructure.DbUpdateException' occurred in EntityFramework.dll but was not handled in user code

Additional information: An error occurred while updating the entries. See the inner exception for details.

当我检查详细信息时，“类别”表和“难度”表似乎为空，但其他字段都包含我提供的信息。

My Database Schema is the following:

Category connects to Word and Difficulty connects to Word.

Both Category and Difficulty are a 1 to many relationship with the table Word.

Answer 1

如果您使用的是 Entity Framework ，则需要在模型中定义约束，有 2 个选项，代码优先或数据库优先

这里是我先用数据库的例子

Database First

从数据库生成模型后，使用脚手架创建创建更新删除的简单步骤

Scaffolding crud

有了脚手架，你更容易创建 crud，如果有任何限制的话

上面的例子你创建工作选择难度/类别是的你的下拉列表将自动创建

示例我的代码菜单创建器 Controller

   // GET: SystemMenus/Create
    public IActionResult Create()
    {
        ViewData["ParentId"] = new SelectList(_context.SystemMenus, "Id", "Name");      
        ViewData["Color"] = new SelectList(OptionDropdown.GetBackgroundColor(), "Value", "Text");
        ViewData["Size"] = new SelectList(OptionDropdown.GetSize(), "Value", "Text");
        ViewData["Module"] = new SelectList(OptionDropdown.GetModule(), "Value", "Text");
        return View();
    }

    // POST: SystemMenus/Create
    // To protect from overposting attacks, please enable the specific properties you want to bind to, for 
    // more details see http://go.microsoft.com/fwlink/?LinkId=317598.
    [HttpPost]
    [ValidateAntiForgeryToken]
    public async Task<IActionResult> Create([Bind("Id,Name,Controller,Action,ParentId,Icon,Module,Description,FixHeader,Color,Size")] SystemMenu systemMenu)
    {
        if (ModelState.IsValid)
        {
            _context.Add(systemMenu);
            await _context.SaveChangesAsync();
            return RedirectToAction(nameof(Index));
        }
        ViewData["ParentId"] = new SelectList(_context.SystemMenus, "Id", "Name", systemMenu.ParentId);
        ViewData["Color"] = new SelectList(OptionDropdown.GetBackgroundColor(), "Value", "Text", systemMenu.Color);
        ViewData["Size"] = new SelectList(OptionDropdown.GetSize(), "Value", "Text", systemMenu.Size);
        ViewData["Module"] = new SelectList(OptionDropdown.GetModule(), "Value", "Text", systemMenu.Module);
        return View(systemMenu);
    }

这里是我的带有递归约束 parentid 的模型

 public class SystemMenu
{
    public SystemMenu()
    {
        Details = new HashSet<SystemMenu>();
    }


    [Key]
    public int Id { get; set; }

    [StringLength(50)]
    public string Name { get; set; }

    [StringLength(50)]
    public string Controller { get; set; }
    [StringLength(50)]
    public string Action { get; set; }

    [ForeignKey("ParentId")]

    public SystemMenu Parent { get; set; }
    [Display(Name = "Parent")]
    public int? ParentId { get; set; }
    [StringLength(50)]
    public string Icon { get; set; }

    [StringLength(50)]
    public string Module { get; set; }

    [StringLength(200)]
    [DataType(DataType.MultilineText)]
    public string Description { get; set; }
    public bool FixHeader { get; set; }

    [StringLength(50)]
    public string Color { get; set; }

    [StringLength(50)]
    public string Size { get; set; }

    public ICollection<SystemMenu> Details { get; set; }
}

这是我的看法

enter code 

@model NCFramework.Models.System.SystemMenu

@{
    ViewData["Title"] = "Create";
    Layout = "~/Views/Shared/_Layout.cshtml";
}

<div class="row">
    <div class="col-md-4">
        <form asp-action="Create">
            <div asp-validation-summary="ModelOnly" class="text-danger"></div>
            <div class="form-group">
                <label asp-for="Name" class="control-label"></label>
                <input asp-for="Name" class="form-control" />
                <span asp-validation-for="Name" class="text-danger"></span>
            </div>
            <div class="form-group">
                <label asp-for="Controller" class="control-label"></label>
                <input asp-for="Controller" class="form-control" />
                <span asp-validation-for="Controller" class="text-danger"></span>
            </div>
            <div class="form-group">
                <label asp-for="Action" class="control-label"></label>
                <input asp-for="Action" class="form-control" />
                <span asp-validation-for="Action" class="text-danger"></span>
            </div>
            <div class="form-group">
                <label asp-for="ParentId" class="control-label"></label>
                <select asp-for="ParentId" class ="form-control" asp-items="ViewBag.ParentId">
                    <option value="">Select</option>
                </select>
            </div>
            <div class="form-group">
                <label asp-for="Icon" class="control-label"></label>
                <input asp-for="Icon" class="form-control" />
                <span asp-validation-for="Icon" class="text-danger"></span>
            </div>
            <div class="form-group">
                <label asp-for="Module" class="control-label"></label>
                <select asp-for="Module" class="form-control" asp-items="ViewBag.Module">
                    <option value="">Select</option>
                </select>
                <span asp-validation-for="Module" class="text-danger"></span>
            </div>
            <div class="form-group">
                <label asp-for="Description" class="control-label"></label>
                <input asp-for="Description" class="form-control" />
                <span asp-validation-for="Description" class="text-danger"></span>
            </div>
            <div class="form-group">
                <div class="mt-checkbox-list">
                    <label class="mt-checkbox mt-checkbox-outline">
                        @Html.DisplayNameFor(model => model.FixHeader)
                        <input asp-for="FixHeader" class="checkbox-inline" />
                        <span></span>
                    </label>
                </div>
            </div>
            <div class="form-group">
                <label asp-for="Color" class="control-label"></label>
                <select asp-for="Color" class="form-control" asp-items="ViewBag.Color">
                    <option value="">Select</option>
                </select>
                <span asp-validation-for="Color" class="text-danger"></span>
            </div>
            <div class="form-group">
                <label asp-for="Size" class="control-label"></label>
                <select asp-for="Size" class="form-control" asp-items="ViewBag.Size">
                    <option value="">Select</option>
                </select>
                <span asp-validation-for="Size" class="text-danger"></span>
            </div>
            <div class="form-group">
                <input type="submit" value="Create" class="btn btn-default" />
            </div>
        </form>
    </div>
</div>

<div>
    <a asp-action="Index">Back to List</a>
</div>

@section Scripts {
    @{await Html.RenderPartialAsync("_ValidationScriptsPartial");}
}

这里

asp.net core mvc 的例子你也可以用 visual studio 试试，这 3 个文件首先通过定义模型的脚手架生成

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干杯