在EF 6中找不到HasOne [英] HasOne not found in EF 6
问题描述
我对Entity Framework还是很陌生,我正在尝试找出关系。我找到了以下代码:
I am very new to Entity Framework and I am trying to figure out relations. I have found this code:
class MyContext : DbContext
{
public DbSet<Post> Posts { get; set; }
public DbSet<Tag> Tags { get; set; }
protected override void OnModelCreating(ModelBuilder modelBuilder)
{
modelBuilder.Entity<PostTag>()
.HasKey(t => new { t.PostId, t.TagId });
modelBuilder.Entity<PostTag>()
.HasOne(pt => pt.Post)
.WithMany(p => p.PostTags)
.HasForeignKey(pt => pt.PostId);
modelBuilder.Entity<PostTag>()
.HasOne(pt => pt.Tag)
.WithMany(t => t.PostTags)
.HasForeignKey(pt => pt.TagId);
}
}
public class Post
{
public int PostId { get; set; }
public string Title { get; set; }
public string Content { get; set; }
public List<PostTag> PostTags { get; set; }
}
public class Tag
{
public string TagId { get; set; }
public List<PostTag> PostTags { get; set; }
}
public class PostTag
{
public int PostId { get; set; }
public Post Post { get; set; }
public string TagId { get; set; }
public Tag Tag { get; set; }
}
编译代码时出现错误:
'EntityTypeConfiguration'不包含
'HasOne'的定义,也没有扩展方法'HasOne'接受类型'的第一个参数
可以找到EntityTypeConfiguration(您
缺少using指令或程序集引用吗?)
'EntityTypeConfiguration' does not contain a definition for 'HasOne' and no extension method 'HasOne' accepting a first argument of type 'EntityTypeConfiguration' could be found (are you missing a using directive or an assembly reference?)
我试图找到它在Google和StackOverflow上使用,但我发现的唯一问题是如何使用它,而不是为什么会出现问题。我真的错过了参考吗?如果是,是哪一个?
I have tried to find it on Google and StackOverflow, but the only things I found was how to use it and not why it gives problems. Do I actually miss a reference? If so, which one?
推荐答案
HasOne()
是实体框架核心方法。
HasOne()
is an Entity Framework Core method.
在以前的版本中,您使用 HasOptional()
或 HasRequired()
。
In prior versions you use HasOptional()
or HasRequired()
.
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