【配置关系】—Entity Framework实例详解
实体间的关系，简单来说无非就是一对一、一对多、多对多，根据方向性来说又分为双向和单向。Code First在实体关系上有以下约定：
1. 两个实体，如果一个实体包含一个引用属性，另一个实体包含一个集合属性，Code First默认约定它们为一对多关系。
2. 两个实体，如果只有一个实体包含一个导航属性或一个集合属性，Code First也默认约定它们是一对多关系。
3. 两个实体分别包含一个集合属性，Code First默认约定它们为多对多关系。
4. 两个实体分别包含一个引用属性，Code First默认约定它们为一对一关系。
5. 在一对一关系情况下，需要提供给Code First额外的信息，以确定它们的主从关系。
6. 在实体中定义一个外键属性，Code First使用属性是否为空来确定关系是必须还是可选。
一、一对一
在Code First中，一对一关系总是需要配置，因为两个实体都包含有一个引用属性，无法确定它们的主从关系。
配置一对一关系常用的方法：
HasRequired ,HasOptional ,WithOptional ,WithRequiredPrincipal,WithRequiredDependent
下面是用到的类：
1: public class Person
2: {
3: public int PersonId { get; set; }
4: public int SocialSecurityNumber { get; set; }
5: public string FirstName { get; set; }
6: public string LastName { get; set; }
7: public byte[] RowVersion { get; set; }
8: public PersonPhoto Photo { get; set; }
9: }
10:
11: public class PersonPhoto
12: {
13: public int PersonId { get; set; }
14: public byte[] Photo { get; set; }
15: public string Caption { get; set; }
16: public Person PhotoOf { get; set; }
17: }
因为Photo是具体人的，所以PersonPhoto使用PersonId作为主键。
下面是一对一关系配置的几种情况：
1.PersonPhoto必须属于一个Person，但是Person不一定有PersonPhoto，这种关系是1:0..1，此种情况下Person是一定存在的，所以它是主从关系主的一方。
1: HasRequired(t => t.PhotoOf).WithOptional(t => t.Photo);
或
1: HasOptional(t => t.Photo).WithRequired(t => t.PhotoOf);
2.PersonPhoto必须属于一个Person，Person也必须有PersonPhoto，这种关系式1:1，此种情况下，两个都一定存在，要确定主从关系，需要使用WithRequiredPrincipal或WithRequiredDependent。
1: HasRequired(t => t.PhotoOf).WithRequiredDependent(t => t.Photo);
或
1: HasRequired(t => t.Photo).WithRequiredPrincipal(t => t.PhotoOf);
上述两种情况都是真实存在的，不真实存在的就不说了。
下面配置一对一关系贴出Demo：
1: public class Person
2: {
3: public int PersonId { get; set; }
4: public int SocialSecurityNumber { get; set; }
5: public string FirstName { get; set; }
6: public string LastName { get; set; }
7: public byte[] RowVersion { get; set; }
8: public PersonPhoto Photo { get; set; }
9: }
10:
11: public class PersonPhoto
12: {
13: public int PersonId { get; set; }
14: public byte[] Photo { get; set; }
15: public string Caption { get; set; }
16: public Person PhotoOf { get; set; }
17: }
18:
19: //配置Person
20: public class PersonConfiguration : EntityTypeConfiguration<Person>
21: {
22: public PersonConfiguration()
23: {
24: //主键
25: HasKey(t => t.PersonId);
26: //并发检查
27: Property(t => t.SocialSecurityNumber).HasDatabaseGeneratedOption(DatabaseGeneratedOption.None).IsConcurrencyToken();
28: //长度50 不为空
29: Property(t => t.FirstName).IsRequired().HasMaxLength(50);
30: //长度50 不为空
31: Property(t => t.LastName).IsRequired().HasMaxLength(50);
32: //并发检查
33: Property(t => t.RowVersion).IsRowVersion();
34: //HasRequired(t => t.Photo).WithRequiredPrincipal(t => t.PhotoOf);
35: //HasOptional(t => t.Photo).WithRequired(t => t.PhotoOf);
36: }
37: }
38:
39: //配置PersonPhoto
40: public class PersonPhotoConfiguration : EntityTypeConfiguration<PersonPhoto>
41: {
42: public PersonPhotoConfiguration()
43: {
44: //主键
45: HasKey(t => t.PersonId);
46: //长度50
47: Property(t => t.Caption).HasMaxLength(50);
48: //必须从属于Person
49: HasRequired(t => t.PhotoOf).WithRequiredDependent(t => t.Photo);
50: }
51: }
52:
53: public class BreakAwayContext : DbContext
54: {
55: public DbSet<Person> People { get; set; }
56: public DbSet<PersonPhoto> Photos { get; set; }
57:
58: protected override void OnModelCreating(DbModelBuilder modelBuilder)
59: {
60: modelBuilder.Configurations.Add(new PersonConfiguration());
61: modelBuilder.Configurations.Add(new PersonPhotoConfiguration());
62: base.OnModelCreating(modelBuilder);
63: }
64: }
65:
66: public class Initializer : DropCreateDatabaseAlways<BreakAwayContext>
67: {
68: public Initializer()
69: {
70: }
71:
72: //创建数据库时 Seed数据
73: protected override void Seed(BreakAwayContext context)
74: {
75: context.People.Add(new Person()
76: {
77: FirstName = "E",
78: LastName = "F",
79: SocialSecurityNumber = 123456,
80: Photo = new PersonPhoto()
81: {
82: Caption = "这是照片",
83: Photo = new byte[] { }
84: }
85: });
86: context.SaveChanges();
87: }
88: }
测试程序
1: [TestClass]
2: public class UnitTest1
3: {
4: [TestMethod]
5: public void ShouldReturnAPersonWithPhoto()
6: {
7: //Arrange
8: var init = new Initializer();
9: Person person;
10: using (var context = new BreakAwayContext())
11: {
12: init.InitializeDatabase(context);
13: //Act
14: person = context.People.Include(t => t.Photo).FirstOrDefault();
15: }
16: //Assert
17: Assert.IsNotNull(person);
18: Assert.IsNotNull(person.Photo);
19: }
20: }
测试结果：
二、一对多
下面是用到的类：
1: public class Blog
2: {
3: public Blog()
4: {
5: Posts = new List<Post>();
6: }
7:
8: public int Id { get; set; }
9: public DateTime Creationdate { get; set; }
10: public string ShortDescription { get; set; }
11: public string Title { get; set; }
12: public List<Post> Posts { get; set; }
13: }
14:
15: public class Post
16: {
17: public int Id { get; set; }
18: public string Title { get; set; }
19: public string Content { get; set; }
20: public DateTime PostedDate { get; set; }
21:
22: public Nullable<int> BlogId { get; set; }
23: public virtual Blog Blog { get; set; }
24:
25: public int PrimaryAuthorId { get; set; }
26: public virtual Author PrimaryAuthor { get; set; }
27: public Nullable<int> SecondaryAuthorId { get; set; }
28: public virtual Author SecondaryAuthor { get; set; }
29: }
30:
31: public class Author
32: {
33: public int Id { get; set; }
34: public string Name { get; set; }
35: public string Email { get; set; }
36: //个人简历
37: public string Bio { get; set; }
38:
39: public List<Post> PrimaryAuthorFor { get; set; }
40: public List<Post> SecondaryAuthorFor { get; set; }
41: }
配置一对多关系常用的方法有：
HasOptional ,HasRequired ,HasMany
Has方法后面往往跟着With方法
WithOptional ,WithRequired ,WithMany
下面配置一对多的几种情况：
1.Post一定归属于一个Blog，这种关系是1:n。
1: HasMany(x => x.Posts).WithRequired(x =>x.Blog)
或
1: HasRequired(x => x.Blog).WithMany(x => x.Posts)
2.Post可以单独存在，不用归属于Blog，这种关系是0..1:n。
1: HasMany(x => x.Posts).WithOptional(x => x.Blog)
或
1: HasOptional(x => x.Blog).WithMany(x => x.Posts)
设置外键
外键的默认约定：
[Target Type Key Name], [Target Type Name] + [Target Type Key Name], or [Navigation
Property Name] + [Target Type Key Name]
本例中，匹配的是[Target Type Name] + [Target Type Key Name]，目标类型是Blog，目标类型主键是Id，加起来就是BlogId。下面使用Fluent API显示设置外键：
1: HasMany(x => x.Posts).WithOptional(x => x.Blog).HasForeignKey(x => x.BlogId)
设置级联删除
1: HasMany(x => x.Posts).WithOptional(x => x.Blog).HasForeignKey(x => x.BlogId).WillCascadeOnDelete();
反转属性
在Post实体中，有两个属性：PrimaryAuthor和SecondaryAuthor，第一作者和第二作者。在Author中有两个集合属性，Code First默认不能确定哪个集合属性和Post中的导航属性相匹配。使用Fluent API配置反转属性，如下：
1: HasRequired(t => t.PrimaryAuthor).WithMany(t => t.PrimaryAuthorFor);
2: HasOptional(t => t.SecondaryAuthor).WithMany(t => t.SecondaryAuthorFor);
下面是配置一对多关系的Demo:
1: public class Blog
2: {
3: public Blog()
4: {
5: Posts = new List<Post>();
6: }
7:
8: public int Id { get; set; }
9: public DateTime Creationdate { get; set; }
10: public string ShortDescription { get; set; }
11: public string Title { get; set; }
12: public List<Post> Posts { get; set; }
13: }
14:
15: public class Post
16: {
17: public int Id { get; set; }
18: public string Title { get; set; }
19: public string Content { get; set; }
20: public DateTime PostedDate { get; set; }
21:
22: //Post可以不归属到Blog独立存在，注意这里的外键属性要设置为可空的
23: public Nullable<int> BlogId { get; set; }
24: public virtual Blog Blog { get; set; }
25:
26: public int PrimaryAuthorId { get; set; }
27: public virtual Author PrimaryAuthor { get; set; }
28: public Nullable<int> SecondaryAuthorId { get; set; }
29: public virtual Author SecondaryAuthor { get; set; }
30: }
31:
32: public class Author
33: {
34: public int Id { get; set; }
35: public string Name { get; set; }
36: public string Email { get; set; }
37: //个人简历
38: public string Bio { get; set; }
39:
40: public List<Post> PrimaryAuthorFor { get; set; }
41: public List<Post> SecondaryAuthorFor { get; set; }
42: }
43:
44: public class BlogConfiguratioin : EntityTypeConfiguration<Blog>
45: {
46: public BlogConfiguratioin()
47: {
48: ToTable("Blogs");
49: HasKey(t => t.Id);
50: Property(t => t.Id).HasDatabaseGeneratedOption(DatabaseGeneratedOption.Identity);
51: Property(t => t.Title).IsRequired().HasMaxLength(250);
52: Property(t => t.Creationdate).HasColumnName("CreationDate").IsRequired();
53: Property(t => t.ShortDescription).HasColumnType("Text").IsMaxLength().IsOptional().HasColumnName("Description");
54: //配置Blog和Post的一对多关系，Blog对Post是可选的，外键BlogId，并设置为级联删除
55: HasMany(t => t.Posts).WithOptional(t => t.Blog).HasForeignKey(t => t.BlogId).WillCascadeOnDelete();
56: }
57: }
58:
59: public class PostConfiguration : EntityTypeConfiguration<Post>
60: {
61: public PostConfiguration()
62: {
63: ToTable("Posts");
64: HasKey(t => t.Id);
65: Property(t => t.Id).HasColumnName("PostId").HasDatabaseGeneratedOption(DatabaseGeneratedOption.Identity);
66: Property(t => t.Content).HasColumnName("Body").IsMaxLength();
67: Property(t => t.PostedDate).HasColumnName("PostedDate");
68: Property(t => t.Title).HasColumnName("Title").IsMaxLength();
69: //配置反转属性，集合属性PrimaryAuthorFor匹配PrimaryAuthor
70: HasRequired(t => t.PrimaryAuthor).WithMany(t => t.PrimaryAuthorFor);
71: //配置反转属性,集合属性SecondaryAuthorFor匹配SecondaryAuthor
72: HasOptional(t => t.SecondaryAuthor).WithMany(t => t.SecondaryAuthorFor);
73: }
74: }
75:
76: public class AuthorConfiguration : EntityTypeConfiguration<Author>
77: {
78: public AuthorConfiguration()
79: {
80: ToTable("Authors");
81: HasKey(t => t.Id).Property(t => t.Id).HasColumnName("AuthorId").HasDatabaseGeneratedOption(DatabaseGeneratedOption.Identity);
82: Property(t => t.Name).IsRequired().HasMaxLength(50);
83: Property(t => t.Email).IsRequired().HasMaxLength(50);
84: Property(t => t.Bio).HasMaxLength(1000);
85: }
86: }
87:
88: public class BreakAwayContext : DbContext
89: {
90: public DbSet<Blog> Blogs { get; set; }
91: public DbSet<Post> Posts { get; set; }
92: public DbSet<Author> Authors { get; set; }
93:
94: protected override void OnModelCreating(DbModelBuilder modelBuilder)
95: {
96: modelBuilder.Configurations.Add(new BlogConfiguratioin());
97: modelBuilder.Configurations.Add(new PostConfiguration());
98: modelBuilder.Configurations.Add(new AuthorConfiguration());
99: base.OnModelCreating(modelBuilder);
100: }
101: }
102:
103: public class Initializer : DropCreateDatabaseAlways<BreakAwayContext>
104: {
105: public Initializer()
106: {
107: }
108:
109: protected override void Seed(BreakAwayContext context)
110: {
111: var primaryAuthor = new Author()
112: {
113: Name = "张三",
114: Email = "zhangsan@126.com",
115: Bio = "张三的简历"
116: };
117: var secondaryAuthor = new Author()
118: {
119: Name = "李四",
120: Email = "lisi@126.com",
121: Bio = "李四的简历"
122: };
123: var blog = new Blog()
124: {
125: Title = "EF",
126: ShortDescription = "关于EF的博客",
127: Creationdate = DateTime.Now
128: };
129: blog.Posts.Add(new Post()
130: {
131: Title = "配置关系",
132: PostedDate = DateTime.Now,
133: Content = "这是Post的内容",
134: PrimaryAuthor = primaryAuthor,
135: SecondaryAuthor = secondaryAuthor
136: });
137: context.Blogs.Add(blog);
138: context.SaveChanges();
139: }
140: }
测试程序：
1: [TestClass]
2: public class OneToManyTest
3: {
4: [TestMethod]
5: public void ShouldReturnBlogWithPosts()
6: {
7: //Arrage
8: Database.SetInitializer(new Initializer());
9: var context = new BreakAwayContext();
10: //Act
11: var blog = context.Blogs.Include(t => t.Posts).FirstOrDefault();
12: //Assert
13: Assert.IsNotNull(blog);
14: Assert.IsNotNull(blog.Posts);
15: Assert.IsNotNull(blog.Posts.FirstOrDefault().PrimaryAuthor);
16: }
17: }
测试结果：
三、多对多
下面是配置多对多关系用到的类，跟一对多差不多，只不过Post和Author的关系变成多对多的了。
1: public class Post
2: {
3: public int Id { get; set; }
4: public string Title { get; set; }
5: public string Content { get; set; }
6: public DateTime PostedDate { get; set; }
7:
8: public virtual List<Author> Authors { get; set; }
9: }
10:
11: public class Author
12: {
13: public int Id { get; set; }
14: public string Name { get; set; }
15: public string Email { get; set; }
16: //个人简历
17: public string Bio { get; set; }
18:
19: public virtual List<Post> Posts { get; set; }
20: }
一篇文章有多个作者，一个作者著有多篇文章。
配置多对多关系使用HasMany和WithMany方法，可以使用Map配置生成关联表的名字。
下面是配置多对多关系的Demo：
1: public class Post
2: {
3: public Post()
4: {
5: Authors = new List<Author>();
6: }
7:
8: public int Id { get; set; }
9: public string Title { get; set; }
10: public string Content { get; set; }
11: public DateTime PostedDate { get; set; }
12:
13: public virtual List<Author> Authors { get; set; }
14: }
15:
16: public class Author
17: {
18: public Author()
19: {
20: Posts = new List<Post>();
21: }
22:
23: public int Id { get; set; }
24: public string Name { get; set; }
25: public string Email { get; set; }
26: //个人简历
27: public string Bio { get; set; }
28:
29: public virtual List<Post> Posts { get; set; }
30: }
31:
32: public class PostConfiguration : EntityTypeConfiguration<Post>
33: {
34: public PostConfiguration()
35: {
36: ToTable("Posts");
37: HasKey(t => t.Id);
38: Property(t => t.Id).HasColumnName("PostId").HasDatabaseGeneratedOption(DatabaseGeneratedOption.Identity);
39: Property(t => t.Content).HasColumnName("Body").IsMaxLength();
40: Property(t => t.PostedDate).HasColumnName("PostedDate");
41: Property(t => t.Title).HasColumnName("Title").IsMaxLength();
42: //配置多对多关系 ToTable 配置生成的关联表名字 MapLeftKey默认表示调用HasMany的实体的主键
43: //本例中如果不使用MapLeftKey默认生成Post_Id
44: HasMany(t => t.Authors).WithMany(t => t.Posts).Map(m =>
45: {
46: m.ToTable("PostAuthor");
47: m.MapLeftKey("PostId");
48: m.MapRightKey("AuthorId");
49: });
50: }
51: }
52:
53: public class AuthorConfiguration : EntityTypeConfiguration<Author>
54: {
55: public AuthorConfiguration()
56: {
57: ToTable("Authors");
58: HasKey(t => t.Id);
59: Property(t => t.Id).HasColumnName("AuthorId").HasDatabaseGeneratedOption(DatabaseGeneratedOption.Identity);
60: Property(t => t.Bio).HasColumnType("Text").IsMaxLength();
61: Property(t => t.Email).HasMaxLength(100).IsRequired();
62: Property(t => t.Name).HasMaxLength(100).IsRequired();
63: }
64: }
65:
66: public class TestContext : DbContext
67: {
68: public DbSet<Post> Posts { get; set; }
69: public DbSet<Author> Authors { get; set; }
70:
71: protected override void OnModelCreating(DbModelBuilder modelBuilder)
72: {
73: modelBuilder.Configurations.Add(new PostConfiguration());
74: modelBuilder.Configurations.Add(new AuthorConfiguration());
75: base.OnModelCreating(modelBuilder);
76: }
77: }
78:
79: public class Initializer : DropCreateDatabaseAlways<TestContext>
80: {
81: protected override void Seed(TestContext context)
82: {
83: var post = new Post()
84: {
85: Title = "Post1",
86: Content = "Content1",
87: PostedDate = DateTime.Now
88: };
89: var author = new Author()
90: {
91: Name = "张三",
92: Email = "zhangsan@126.com",
93: Bio = "张三的简历"
94: };
95: var author1 = new Author()
96: {
97: Name = "李四",
98: Email = "lisi@126.com",
99: Bio = "李四的简历"
100: };
101: var author2 = new Author()
102: {
103: Name = "王五",
104: Email = "wangwu@126.com",
105: Bio = "王五的简历"
106: };
107: post.Authors.Add(author);
108: post.Authors.Add(author1);
109: context.Posts.Add(post);
110: post = new Post()
111: {
112: Title = "Post2",
113: Content = "Content2",
114: PostedDate = DateTime.Now
115: };
116: post.Authors.Add(author);
117: post.Authors.Add(author2);
118: context.Posts.Add(post);
119: context.SaveChanges();
120: }
121: }
测试程序：
1: [TestClass]
2: public class ManyToManyTest
3: {
4: [TestMethod]
5: public void ShouldReturnPostWithAuthors()
6: {
7: //Arrage
8: var init = new Initializer();
9: var context = new ManyToMany.TestContext();
10: init.InitializeDatabase(context);
11: //Act
12: var post = context.Posts.Include(t => t.Authors).FirstOrDefault();
13: //Assert
14: Assert.IsNotNull(post);
15: Assert.AreEqual(2, post.Authors.Count);
16: Assert.AreEqual("李四", post.Authors[1].Name);
17: }
18: }
测试结果：
现在关联表中只有两个字段，如下图所示：
如果再加个字段，比如DateAdd，这就需要给关联表定义一个实体。
1: public class PostAuthor
2: {
3: public int PostId { get; set; }
4: public int AuthorId { get; set; }
5:
6: public Post Post { get; set; }
7: public Author Author { get; set; }
8:
9: public DateTime DateAdd { get; set; }
10: }
另外需要在Post和Author实体中加入一个集合属性：
1: public virtual List<PostAuthor> PostAuthors { get; set; }
另外还需要配置PostAuthor实体，具体代码如下面的Demo所示：
1: public class Post
2: {
3: public Post()
4: {
5: PostAuthors = new List<PostAuthor>();
6: }
7:
8: public int Id { get; set; }
9: public string Title { get; set; }
10: public string Content { get; set; }
11: public DateTime PostedDate { get; set; }
12:
13: //public virtual List<Author> Authors { get; set; }
14: public virtual List<PostAuthor> PostAuthors { get; set; }
15: }
16:
17: public class Author
18: {
19: public Author()
20: {
21: PostAuthors = new List<PostAuthor>();
22: }
23:
24: public int Id { get; set; }
25: public string Name { get; set; }
26: public string Email { get; set; }
27: //个人简历
28: public string Bio { get; set; }
29:
30: //public virtual List<Post> Posts { get; set; }
31: public virtual List<PostAuthor> PostAuthors { get; set; }
32: }
33:
34: //关联表的实体
35: public class PostAuthor
36: {
37: public int PostId { get; set; }
38: public int AuthorId { get; set; }
39:
40: public Post Post { get; set; }
41: public Author Author { get; set; }
42:
43: public DateTime? DateAdd { get; set; }
44: }
45:
46: public class PostConfiguration : EntityTypeConfiguration<Post>
47: {
48: public PostConfiguration()
49: {
50: ToTable("Posts");
51: HasKey(t => t.Id);
52: Property(t => t.Id).HasColumnName("PostId").HasDatabaseGeneratedOption(DatabaseGeneratedOption.Identity);
53: Property(t => t.Content).HasColumnName("Body").IsMaxLength();
54: Property(t => t.PostedDate).HasColumnName("PostedDate");
55: Property(t => t.Title).HasColumnName("Title").IsMaxLength();
56: }
57: }
58:
59: public class AuthorConfiguration : EntityTypeConfiguration<Author>
60: {
61: public AuthorConfiguration()
62: {
63: ToTable("Authors");
64: HasKey(t => t.Id);
65: Property(t => t.Id).HasColumnName("AuthorId").HasDatabaseGeneratedOption(DatabaseGeneratedOption.Identity);
66: Property(t => t.Bio).HasColumnType("Text").IsMaxLength();
67: Property(t => t.Email).HasMaxLength(100).IsRequired();
68: Property(t => t.Name).HasMaxLength(100).IsRequired();
69: }
70: }
71:
72: //配置关联表实体
73: public class PostAuthorConfiguration : EntityTypeConfiguration<PostAuthor>
74: {
75: public PostAuthorConfiguration()
76: {
77: ToTable("PostAuthors");
78: //配置组合主键
79: HasKey(t => new { t.PostId, t.AuthorId });
80: Property(t => t.PostId).HasColumnOrder(0);
81: Property(t => t.AuthorId).HasColumnOrder(1);
82: //这里是配置一对多关系
83: HasRequired(t => t.Post).WithMany(t => t.PostAuthors).HasForeignKey(t => t.PostId);
84: HasRequired(t => t.Author).WithMany(t => t.PostAuthors).HasForeignKey(t => t.AuthorId);
85: }
86: }
87:
88: public class TestContext : DbContext
89: {
90: public DbSet<Post> Posts { get; set; }
91: public DbSet<Author> Authors { get; set; }
92: public DbSet<PostAuthor> PostAuthors { get; set; }
93:
94: protected override void OnModelCreating(DbModelBuilder modelBuilder)
95: {
96: modelBuilder.Configurations.Add(new PostConfiguration());
97: modelBuilder.Configurations.Add(new AuthorConfiguration());
98: modelBuilder.Configurations.Add(new PostAuthorConfiguration());
99: base.OnModelCreating(modelBuilder);
100: }
101: }
102:
103: public class Initializer : DropCreateDatabaseAlways<TestContext>
104: {
105: protected override void Seed(TestContext context)
106: {
107: var post = new Post()
108: {
109: Title = "Post1",
110: Content = "Content1",
111: PostedDate = DateTime.Now
112: };
113: post = context.Posts.Add(post);
114: var author = new Author()
115: {
116: Name = "张三",
117: Email = "zhangsan@126.com",
118: Bio = "张三的简历"
119: };
120: var author1 = new Author()
121: {
122: Name = "李四",
123: Email = "lisi@126.com",
124: Bio = "李四的简历"
125: };
126: author = context.Authors.Add(author);
127: author1 = context.Authors.Add(author1);
128: context.SaveChanges();
129: PostAuthor pa1 = new PostAuthor()
130: {
131: PostId = post.Id,
132: AuthorId = author.Id,
133: DateAdd = DateTime.Now
134: };
135: PostAuthor pa2 = new PostAuthor()
136: {
137: PostId = post.Id,
138: AuthorId = author1.Id,
139: DateAdd = DateTime.Now
140: };
141: context.PostAuthors.Add(pa1);
142: context.PostAuthors.Add(pa2);
143: context.SaveChanges();
144: }
145: }
测试程序：
1: [TestMethod]
2: public void ShouldReturnAuthorsWithDateAdd()
3: {
4: //Arrage
5: var init = new Initializer();
6: var context = new ManyToMany.TestContext();
7: init.InitializeDatabase(context);
8: //Act
9: var post = context.Posts.Include(t => t.PostAuthors).FirstOrDefault();
10: //Assert
11: Assert.IsNotNull(post);
12: Assert.AreEqual(2, post.PostAuthors.Count);
13: Assert.IsNotNull(post.PostAuthors[0].DateAdd);
14: }
测试结果：
生成的关联表如下图所示：
http://www.cnblogs.com/nianming/archive/2012/11/12/2767089.html
【配置关系】—Entity Framework实例详解的更多相关文章
- Entity Framework实例详解
Entity Framework Code First的默认行为是使用一系列约定将POCO类映射到表.然而,有时候,不能也不想遵循这些约定,那就需要重写它们.重写默认约定有两种方式:Data Anno ...
- 转：【工欲善其事必先利其器】—Entity Framework实例详解
开始本篇文章之前,先说一下Entity Framework 6 Alpha1在NuGet中已可用,原文链接http://blogs.msdn.com/b/adonet/archive/2012/10/ ...
- 【配置属性】—Entity Framework实例详解
Entity Framework Code First的默认行为是使用一系列约定将POCO类映射到表.然而,有时候,不能也不想遵循这些约定,那就需要重写它们.重写默认约定有两种方式:Data Anno ...
- —Entity Framework实例详解
Entity Framework Code First的默认行为是使用一系列约定将POCO类映射到表.然而,有时候,不能也不想遵循这些约定,那就需要重写它们.重写默认约定有两种方式:Data Anno ...
- 【迁移】—Entity Framework实例详解 转
一.Entity Framework 迁移命令(get-help EntityFramework) Enable-Migrations 启用迁移 Add-Migration 为挂起的Model变化添加 ...
- 【迁移】—Entity Framework实例详解
好久没有在博客园更新博客了,如今都换了新公司.前段时间写了关于EF迁移的文档,今天拿出来作为这个系列的一篇吧. 一.Entity Framework 迁移命令(get-help EntityFrame ...
- [转]C#综合揭秘——Entity Framework 并发处理详解
本文转自:http://www.cnblogs.com/leslies2/archive/2012/07/30/2608784.html 引言 在软件开发过程中,并发控制是确保及时纠正由并发操作导致的 ...
- Linq实战 之 Linq to Sql及Entity Framework操作详解
Linq实战 之 Linq to Sql及Entity Framework操作详解 一:linq to db的框架 1. linq to sql 2. linq to ado.net entity f ...
- C#综合揭秘——Entity Framework 并发处理详解
引言 在软件开发过程中,并发控制是确保及时纠正由并发操作导致的错误的一种机制.从 ADO.NET 到 LINQ to SQL 再到如今的 ADO.NET Entity Framework,.NET 都 ...
随机推荐
- java面向抽象编程样例
import java.util.*; abstract class Geometry{ public abstract double getArea(); } class Pillar ...
- 【Luogu】P3628特别行动队（斜率优化DP）
题目链接 设c[i]是战斗力前缀和,f[i]是考虑前i个,且最后一组分到第i个士兵为止的战斗力之和 则有朴素状态转移方程 ;i<=n;++i) ;j<i;++j){ int x=c[i]- ...
- [无趣]bit reverse
真不想承认啊,因为年轻而犯下的错误! inline void _BR(int* a,int r){ for(int i=0,j=1;i<r;++i,j<<=1){ for(int k ...
- bzoj 4401 块的计数 思想+模拟+贪心
块的计数 Time Limit: 10 Sec Memory Limit: 256 MBSubmit: 455 Solved: 261[Submit][Status][Discuss] Descr ...
- poj 3304 判断是否存在一条直线与所有线段相交
Segments Time Limit: 1000MS Memory Limit: 65536K Total Submissions: 8579 Accepted: 2608 Descript ...
- 巴厘岛的雕塑 BZOJ 4069
巴厘岛的雕塑 题解: 题意是要求分组使每组的和按位取或的值最小 那么考虑贪心,尽量使高位为0 于是枚举位置,从最高位枚举 假设当前枚举到第l位. 令 f[i][j] 表示前 i 个数分成 j 组,满足 ...
- angular中多控制器的依赖注入写法
直接看图,每个控制器有自己的名称,第二个参数中有需要注入的依赖对象,最后是我们的自定义函数,这样我们可以以模块化的方式进行书写.
- POJ 2125 最小点权覆盖集（输出方案）
题意:给一个图(有自回路,重边),要去掉所有边,规则:对某个点,可以有2种操作:去掉进入该点 的所有边,也可以去掉出该点所有边,(第一种代价为w+,第二种代价为w-).求最小代价去除所有边. 己思:点 ...
- android 活动
一.Activity 声明周期 1 创建 把页面上的个元素加载到内存 onCreate 2 开始 把页面显示到屏幕 onStart 3 恢复 让页面在屏幕活动 onResume 4 暂停 停止页面动作 ...
- 面试题：oracle数据库行转列的问题
今天我一个学弟问了一个面试题: 有表A,结构如下:A: p_ID p_Num s_id1 10 011 12 022 8 013 11 013 8 03其中:p_ID为产品ID,p_Num为产品库存量 ...