更新时违反实体核心的PRIMARY KEY约束错误
在书籍和作者之间通常存在许多对许多的关系。尝试更新作者时出现错误。错误的全名是“ SqlException：违反主键约束'PK_BookAuthor'。无法在对象'dbo.BookAuthor'中插入重复键。重复键值为（2，2）。”。
如果我不使用UpdateAssociatedObject函数，则一切正常。但是，如果使用它，则在尝试保存更改时会收到错误消息。
var parseBook = Mapper.Map<BookViewModel, Book>(viewModel);
Book viewModelBook = parseBook;
var book = db.Books.FindOne(viewModel.BookId);
book.BookId = viewModelBook.BookId;
book.BookName = viewModelBook.BookName;
book.Genre = viewModelBook.Genre;
book.Pages = viewModelBook.Pages;
book.Publisher = viewModelBook.Publisher;
db.SaveChanges();
UpdateAssociatedObject(book, viewModelBook);
}
public void UpdateAssociatedObject(Book bookForUpdate, Book book)
{
bookForUpdate.BookAuthors = book.BookAuthors;
//error is here
db.SaveChanges();
}
映射后viewModelBook的值： 模型（为简洁起见，删除了一些属性）
public class Book
{
public int BookId { get; set; }
public List<BookAuthor> BookAuthors { get; set; }
}
public class Author
{
public int AuthorId { get; set; }
public string AuthorName { get; set; }
public List<BookAuthor> BookAuthors { get; set; }
}
public class BookAuthor
{
public int BookId { get; set; }
public Book Book { get; set; }
public int AuthorId { get; set; }
public Author Author { get; set; }
}
public class BookViewModel
{
public int BookId { get; set; }
public virtual List<AuthorViewModel> Authors { get; set; }
}
public class AuthorViewModel
{
public int AuthorId { get; set; }
public string AuthorName { get; set; }
}
UPD：创建书籍后，BookId会跳（以1000为步长）。
将Include（）添加到Find方法后，错误更改为
System.InvalidOperationException：无法跟踪实体类型'BookAuthor'的实例，因为已经跟踪了另一个具有相同的{'BookId'，'AuthorId'}关键字值的实例。附加现有实体时，请确保仅附加一个具有给定键值的实体实例。考虑使用'DbContextOptionsBuilder.EnableSensitiveDataLogging'来查看冲突的键值。
料青山看我应如是2回答
-
湖上湖
终于成功了！在下面，您可以看到与原始代码的不同之处。PS也许您知道Remove方法更好的算法，如果可以在注释中键入它，那么我将更改答案。BookRepository： public Book Find(int id) { Book searchedBook = db.Books .Include(b => b.BookAuthors) .ThenInclude(b => b.Author) .SingleOrDefault(b => b.BookId == id); return searchedBook; }BookService：public void UpdateObject(BookViewModel viewModel) { Book parsedBook = Mapper.Map<BookViewModel, Book>(viewModel); //Book viewModelBook = parseBook; var book = db.Books.Find(viewModel.BookId); book.BookId = parsedBook.BookId; book.BookName = parsedBook.BookName; book.Genre = parsedBook.Genre; book.Pages = parsedBook.Pages; book.Publisher = parsedBook.Publisher; UpdateAssociatedObject(book, parsedBook); }public void UpdateAssociatedObject(Book bookToUpdate, Book viewModelBook) { AddUpdatedAuthors(bookToUpdate, viewModelBook); RemoveUpdatedAuthors(bookToUpdate, viewModelBook); db.SaveChanges(); } private void AddUpdatedAuthors(Book bookToUpdate, Book viewModelBook) { foreach (var authors in viewModelBook.BookAuthors) { var searchBookAuthor = bookToUpdate.BookAuthors.Find(b => b.AuthorId == authors.AuthorId); if (searchBookAuthor == null) { bookToUpdate.BookAuthors.Add(authors); } } } private void RemoveUpdatedAuthors(Book bookToUpdate, Book viewModelBook) { int countOfAuthors = bookToUpdate.BookAuthors.Count; for (int i = 0; i < countOfAuthors; i++) { BookAuthor searchBookAuthor = null; foreach (var viewModelAuthors in viewModelBook.BookAuthors) { if (viewModelAuthors.AuthorId == bookToUpdate.BookAuthors[i].AuthorId) { searchBookAuthor = viewModelAuthors; } } if (searchBookAuthor == null) { bookToUpdate.BookAuthors.Remove(bookToUpdate.BookAuthors[i]); i--; countOfAuthors--; } } } -
婷婷同学_
该问题出现在db.SaveChanges（）中。您在相同的上下文中多次调用db.SaveChangesdb.SaveChanges(); UpdateAssociatedObject(book, viewModelBook);然后UpdateAssociatedObject(book, viewModelBook); 尝试删除一个db.SaveChanges（）。
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