Question

我有控制器方法来添加一本书：

[HttpPost()]
public IActionResult AddBook([FromBody] BookPL book)
{
    if (!ModelState.IsValid)
    {
        return StatusCode(400, "Model is not valid");
    }

    try
    {
        book.BookId = Guid.NewGuid();
        var newBook = mapper.Map<BookDto>(book);
        booksService.AddBook(newBook);
        return StatusCode(201, "Book was added");
    }
    catch (Exception ex)
    {
        return StatusCode(500, "Internal server error. Book is not added. Exception message: " + ex);
    }
}

在图书服务中，它从BookDto映射到EF模型：

public class Book
{
    public Guid BookId { get; set; } 
    public bool IsAvailable { get; set; }
    public virtual Category Category { get; set; }
    public virtual Author Author { get; set; }

    [Required]
    [MaxLength(150, ErrorMessage = "Name length must be less then 150 characters")]
    public string Name { get; set; }
    [Required]
    [MaxLength(2500, ErrorMessage = "Description length must be less then 2500 characters")]
    public string Description { get; set; }   

}

问题是，我无法添加书，EF对此有异议：

Microsoft.Data.SqlClient.SqlException（0x80131904）：违反主键约束'PK_Authors'。无法在其中插入重复的密钥对象“ dbo.Authors”。重复的键值为（94cf4d6a-b6bc-4015-acee-2345438ee912）。该声明已经终止。

但是当出现异常时，如何使用现有作者和类别添加新书？

Answer 1

在bookservice.addbook或自动映射器配置文件中，仅将书籍的AuthorId设置为不是整个Author实体（将其设置为null），或将Author的实体标记为不变。

            context.Entry(book.Author).State = EntityState.Unchanged;
            context.Entry(book.Category).State = EntityState.Unchanged;

您的图书实体应具有CategoryId和AuthorId

Answer 2

错误很明显，您正在尝试插入具有现有ID的书。问题可能出在Guid生成器或mapper。

如何通过EF Core将复杂的类对象添加到DB，对象是从客户端获取的

2 个答案: