一对一
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public class Blog { public int BlogId { get; set; } public string Url { get; set; } public BlogImage BlogImage { get; set; } } public class BlogImage { public int BlogImageId { get; set; } public byte[] Image { get; set; } public string Caption { get; set; } public int BlogId { get; set; } public Blog Blog { get; set; } } |
一对多
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public class Blog { public int BlogId { get; set; } public string Url { get; set; } public List<Post> Posts { get; set; } } public class Post { public int PostId { get; set; } public string Title { get; set; } public string Content { get; set; } public int BlogId { get; set; } public Blog Blog { get; set; } } |
多对多
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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; } } |
关于包含include说明：
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public class Product { public int Id { get; set; } public string BarCode { get; set; } public int CategoryId { get; set; } = 0; public Category Category { get; set; } public Clothing Clothing { get; set; } } public class Category { public int Id { get; set; } public string CategoryName { get; set; } } public class Clothing { public int Id { get; set; } public string Brand { get; set; } public int ProductId { get; set; } = 0; public Product Product { get; set; } } |
Product与Category和Clothing都是一对一关系，只是导航属性不同。
如果Product访问Clothing需要使用Include包含进来，否则Clothing为空，而Category同理。
var q=dbcontext.Product;//可访问关联的Category表信息而Clothing=null
var q=dbcontext.Product.Include(p=>p.Clothing);//可Category=null和Cloning关联的信息
var q=dbcontext.Product.Include(p => p.Clothing).Include(p=>p.Category);//这样就关联起来了。
参考：https://docs.microsoft.com/zh-cn/ef/core/modeling/relationships
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2022-05-30 下午5:27
2022-05-30 下午5:27