SqlException: INSERT 語句與 FOREIGN KEY 約束沖突，首先使用 EF 代碼 C#

Question

每次單擊“添加產品”時，都會出現以下錯誤。 我將非常感謝有關為什么我收到此錯誤的任何提示

SqlException: INSERT 語句與 FOREIGN KEY 約束“FK_Products_Categories_CategoryId”沖突。 沖突發生在數據庫“eCommerce”、表“dbo.Categories”、“CategoryId”列中。 該語句已終止。

主頁視圖：

                <div class="collapse navbar-collapse" id="bs-example-navbar-collapse-1">
                    <ul class="nav navbar-nav">
    <li><a asp-controller="Home" asp-action="Index">Home</a></li>

    <li><a asp-controller="Product" asp-action="AddProduct">Add product</a></li>
    enter code here
                     </ul>
                </div>

AppDbContext.cs

    public class AppDbContext : IdentityDbContext<IdentityUser>
    {
        public AppDbContext(DbContextOptions<AppDbContext> options) : base(options)
        {

        }
        public DbSet<Category> Categories { get; set; }
        public DbSet<Product> Products { get; set; }
    }

我的模型：Product.cs 和 Category.cs 模型：

  public class Product
    {
        public int ProductId { get; set; }                
        public string Name { get; set; }
        public string ShortDescription { get; set; }
        public string LongDescription { get; set; }
        public decimal Price { get; set; }
        public string ImageUrl { get; set; }
        public string ImageThumbnailUrl { get; set; }
        public bool IsProductOfTheWeek { get; set; }
        public bool InStock { get; set; }
        public int CategoryId { get; set; }
        public Category Category { get; set; }
    }

    public class Category
    {
        public int CategoryId { get; set; }
        public string CategoryName { get; set; }
        public string Description { get; set; }
        public List<Product> Products { get; set; }
    }

我的控制器：Productontroller.cs

        [HttpPost]
        public IActionResult AddProduct(Product product)
        {
            if (ModelState.IsValid)
            {
                _appDbContext.Products.Add(product);  
                _appDbContext.SaveChanges();            
                return RedirectToAction("SeedComplete");
            }

            return View(product);
        }


        public IActionResult SeedComplete()
        {
            ViewBag.SeedCompleteMessage = "Thanks for adding the product!";

            return View();
        }

我的觀點：AddProduct.cshtml

@model Product

    <form asp-action="AddProduct" method="post" class="form-horizontal" role="form">
        <h4>You're just one step away.</h4>

        <div asp-validation-summary="All" class="text-danger"></div>

        <div class="form-group">
            <label asp-for="Name" class="col-md-2 control-label"></label>
            <div class="col-md-5">
                <input asp-for="Name" class="form-control" />
                <span asp-validation-for="Name" class="text-danger"></span>
            </div>
        </div>

        <div class="form-group">
            <label asp-for="Price" class="col-md-2 control-label"></label>
            <div class="col-md-5">
                <input asp-for="Price" class="form-control" />
                <span asp-validation-for="Price" class="text-danger"></span>
            </div>
        </div>

        <div class="form-group">
            <label asp-for="ShortDescription" class="col-md-2 control-label"></label>
            <div class="col-md-5">
                <input asp-for="ShortDescription" class="form-control" />
                <span asp-validation-for="ShortDescription" class="text-danger"></span>
            </div>
        </div>

        <div class="form-group">
            <label asp-for="LongDescription" class="col-md-2 control-label"></label>
            <div class="col-md-5">
                <input asp-for="LongDescription" class="form-control" />
                <span asp-validation-for="LongDescription" class="text-danger"></span>
            </div>
        </div>

        <div class="form-group">
            <label asp-for="ImageUrl" class="col-md-2 control-label"></label>
            <div class="col-md-5">
                <input asp-for="ImageUrl" class="form-control" />
                <span asp-validation-for="ImageUrl" class="text-danger"></span>
            </div>
        </div>

        <div class="form-group">
            <label asp-for="ImageThumbnailUrl" class="col-md-2 control-label"></label>
            <div class="col-md-5">
                <input asp-for="ImageThumbnailUrl" class="form-control" />
                <span asp-validation-for="ImageThumbnailUrl" class="text-danger"></span>
            </div>
        </div>

        <div class="form-group">
            <label asp-for="IsProductOfTheWeek" class="col-md-2 control-label"></label>
            <div class="col-md-5">
                <input asp-for="IsProductOfTheWeek" class="form-control" />
                <span asp-validation-for="IsProductOfTheWeek" class="text-danger"></span>
            </div>
        </div>

        <div class="form-group">
            <label asp-for="InStock" class="col-md-2 control-label"></label>
            <div class="col-md-5">
                <input asp-for="InStock" class="form-control" />
                <span asp-validation-for="InStock" class="text-danger"></span>
            </div>
        </div>

        <div class="form-group">
            <div class="col-md-offset-2 col-md-5">
                <input id="btn" type="submit" class="btn btn-primary" value="Complete the seed" />
            </div>
        </div>

    </form>

SeedComplete.cshtml：

<h1>@ViewBag.SeedCompleteMessage </h1>

Answer 1

我在 cshtml 中沒有看到您將在何處設置 CategoryId，這意味着它可能會設置為 0，這會導致違反外鍵約束。

在此行的控制器代碼中設置斷點：

_appDbContext.Products.Add(product); 

並查看 CategoryId 是否為 0。