我无法在Entity Framework Core中播种数据

Question

I cannot seed data in my webapp and don't know what's the problem. The app works fine and the user can add data to the database. I have added the saveChanges method but no results. I think I'm sending null data to the database but I can't find the problem. My files: DbContext

 public class BookDbContext: DbContext
{
    public BookDbContext(DbContextOptions options): base(options)
    {

    }

    public DbSet<Books> Books { get; set; }
}

SeedBooks

public static void Initialize(BookDbContext context)
    {
        context.Database.EnsureCreated();

        if (context.Books.Any())
        {
            return;
        }

        var books = new Books[]
         {
        new Books{Id=1, Title ="Kont of Mount Cristos", Description="About eghteen century", Author="Don Mon", Category=Category.aksion},
        new Books{Id=2, Title="Introduction in C Sharp", Description="Learning computer programing", Author="Scott Allen", Category= Category.education},
        new Books{Id=3, Title="The Castle", Description="Learning about history", Author="Ismail Kadare", Category= Category.drama},
        new Books{Id=4, Title="Madam Bavary", Description="Love story", Author="Gi de Mopasan", Category= Category.romance}

         };

        foreach (Books b in books)
        {
            context.Books.Add(b);
        }
            context.SaveChanges();

    }

Books file

public enum Category
{
    aksion, drama, romance, education
}
public class Books
{
    public int Id { get; set; }
    [Required]
    public string Title { get; set; }
    [Required]
    [Display(Name = "Autor Name")]
    public string Author { get; set; }
    [Required]
    [MaxLength(80)]
    public string Description { get; set; }
    [Required]
    public Category Category { get; set; }






}

Index file for the Books

 <table class="table">
    @*<thead>
            <tr>
                <th>
                    @Html.DisplayNameFor(model => Model.Author)
                </th>
                <th>
                    @Html.DisplayNameFor(model => model.Title)
                </th>
                <th>
                    @Html.DisplayNameFor(model => model.Category)
                </th>
                <th>
                    @Html.DisplayNameFor(model => model.Description)
                </th>
                <th></th>
            </tr>
        </thead>*@
    <tbody>
        @foreach (var item in Model.Book)
        {
            <tr>
                <td>
                    @Html.DisplayFor(modelItem => item.Author)
                </td>
                <td>
                    @Html.DisplayFor(modelItem => item.Title)
                </td>
                <td>
                    @Html.DisplayFor(modelItem => item.Category)
                </td>
                <td>
                    @Html.DisplayFor(modelItem => item.Description)
                </td>
                <td>
                    <a asp-action="Details" asp-route-id="@item.Id">Details</a>

                </td>
            </tr>
        }
    </tbody>
</table>

<a asp-action="Create" asp-controller="Books">Create</a>

Answer 1

I reproduced your problem with asp.net core mvc with ef core tutorial .

I followed the article and found when you run the project and it will create a database in local and create a student table which contains the data you have initialize.

var context = services.GetRequiredService<SchoolContext>();
DbInitializer.Initialize(context);

However, I found that the table design is as follow:

CREATE TABLE [dbo].[Student] (
    [ID]       INT            IDENTITY (1, 1) NOT NULL,
    [Age]      INT            NOT NULL,
    [LastName] NVARCHAR (MAX) NULL,
    CONSTRAINT [PK_Student] PRIMARY KEY CLUSTERED ([ID] ASC)
);

The ID property has set IDENTITY (1, 1) , which means that you need to add ID when you want to add every data into table.

So delete "IDENTITY(1,1)" and it will work fine.