[英]How to configure many to many relationship using entity framework fluent API
[英]How to configure a Many To Many relationship in Entity Framework Core
我有一些文章和一些作者,并希望将它们链接为:
我使用此教程创建了ManyToMany关系: https : //www.learnentityframeworkcore.com/configuration/many-to-many-relationship-configuration
这是我定义班级的方式。
文章
public class Article
{
[Key]
[DatabaseGenerated(DatabaseGeneratedOption.Identity)]
public int ID { get; set; }
public string Title { get; set; }
public DateTime Date { get; set; }
public ICollection<ArticleAuthor> ArticleAuthors { get; set; }
}
作者
public class Author
{
[Key]
[DatabaseGenerated(DatabaseGeneratedOption.Identity)]
public int ID { get; set; }
[Column(TypeName = "text")] public string Name { get; set; }
[Column(TypeName = "text")] public string Email { get; set; }
public ICollection<ArticleAuthor> ArticleAuthors { get; set; }
}
文章作者
public class ArticleAuthor
{
public int ArticleId { get; set; }
public Article Article { get; set; }
public int AuthorId { get; set; }
public Author Author { get; set; }
}
DbContext
public class AppDbContext : DbContext
{
public AppDbContext(DbContextOptions<AppDbContext> options) : base(options)
{
}
public DbSet<Article> Articles { get; set; }
public DbSet<Author> Authors { get; set; }
public DbSet<ArticleAuthor> ArticleAuthors { get; set; }
protected override void OnModelCreating(ModelBuilder modelBuilder)
{
modelBuilder.Entity<ArticleAuthor>()
.HasKey(bc => new {bc.ArticleId, bc.AuthorId});
modelBuilder.Entity<ArticleAuthor>()
.HasOne(bc => bc.Article)
.WithMany(b => b.ArticleAuthors)
.HasForeignKey(bc => bc.ArticleId);
modelBuilder.Entity<ArticleAuthor>()
.HasOne(bc => bc.Author)
.WithMany(c => c.ArticleAuthors)
.HasForeignKey(bc => bc.AuthorId);
}
}
在运行dotnet ef数据库更新后,按预期创建了表
一切似乎都很好,除了当我尝试通过此服务与作者添加文章时:
服务
// POST: api/Articles
[HttpPost]
public async Task<IActionResult> PostArticle([FromBody] Article article)
{
if (!ModelState.IsValid)
{
return BadRequest(ModelState);
}
_context.Articles.Add(article);
await _context.SaveChangesAsync();
return Ok(article);
}
JSON格式
{
"Title":"Title 2",
"ReadingTime" : 2,
"Date":"01.12.2019",
"Theme": "1",
"ArticleAuthors":[
{
"ID":"1"
}
]
}
当我尝试与作者添加文章时,我一直陷在这个错误中
System.InvalidOperationException:实体类型“ ArticleAuthor”上的属性“ AuthorId”具有临时值。 显式设置一个永久值,或者确保将数据库配置为为此属性生成值。
尝试使用此有效负载,应该需要ArticleId和AuthorId,ArticleId在父类中是隐式的,因此您至少应提供AuthorId:
{
"Title":"Title 2",
"ReadingTime" : 2,
"Date":"01.12.2019",
"Theme": "1",
"ArticleAuthors":[
{
"AuthorId":"1"
}
]
}
声明:本站的技术帖子网页,遵循CC BY-SA 4.0协议,如果您需要转载,请注明本站网址或者原文地址。任何问题请咨询:yoyou2525@163.com.