C# 实体框架fluentapi映射

假设我有这些表：

Role
- RoleId
- Name

UserRole
- UserId
- RoleId

User
- UserId
- Username

UserEmail
- UserId
- EmailId
- IsPrimary

Email
- EmailId
- Address

public class Role {
    public int RoleId { get; set; }
    public string Name { get; set; }
    public virtual ICollection<User> Users { get; set; }
}

public class User {
    public int UserId { get; set; }
    public string Username { get; set; }
    public virtual ICollection<Role> Roles { get; set; }
    public virtual ICollection<UserEmail> UserEmails { get; set; }
}

public class UserEmail {
    public int UserId { get; set; }
    public int EmailId { get; set; }
    public bool IsPrimary { get; set; }
    public virtual User User { get; set; }
    public virtual Email Email { get; set; }
}

public class Email {
    public int EmailId { get; set; }
    public string Address { get; set; }
    public virtual ICollection<UserEmail> UserEmails { get; set; }
}

modelBuilder.Entity<Role>().HasKey(q => q.RoleId);

modelBuilder.Entity<Role>()
    .HasMany(q => q.Users)
    .WithMany(q => q.Roles)
    .Map(q => {
                  q.MapLeftKey("RoleId");
                  q.MapRightKey("UserId");
                  q.ToTable("UserRoles");
              });

modelBuilder.Entity<UserEmail>()
    .HasRequired(q => q.User)
    .WithMany(q => q.UserEmails)
    .HasForeignKey(q => q.EmailId);

现在，我的模型应该是这样的：

Role
- RoleId
- Name

UserRole
- UserId
- RoleId

User
- UserId
- Username

UserEmail
- UserId
- EmailId
- IsPrimary

Email
- EmailId
- Address

public class Role {
    public int RoleId { get; set; }
    public string Name { get; set; }
    public virtual ICollection<User> Users { get; set; }
}

public class User {
    public int UserId { get; set; }
    public string Username { get; set; }
    public virtual ICollection<Role> Roles { get; set; }
    public virtual ICollection<UserEmail> UserEmails { get; set; }
}

public class UserEmail {
    public int UserId { get; set; }
    public int EmailId { get; set; }
    public bool IsPrimary { get; set; }
    public virtual User User { get; set; }
    public virtual Email Email { get; set; }
}

public class Email {
    public int EmailId { get; set; }
    public string Address { get; set; }
    public virtual ICollection<UserEmail> UserEmails { get; set; }
}

modelBuilder.Entity<Role>().HasKey(q => q.RoleId);

modelBuilder.Entity<Role>()
    .HasMany(q => q.Users)
    .WithMany(q => q.Roles)
    .Map(q => {
                  q.MapLeftKey("RoleId");
                  q.MapRightKey("UserId");
                  q.ToTable("UserRoles");
              });

modelBuilder.Entity<UserEmail>()
    .HasRequired(q => q.User)
    .WithMany(q => q.UserEmails)
    .HasForeignKey(q => q.EmailId);

添加一对多关系：

Role
- RoleId
- Name

UserRole
- UserId
- RoleId

User
- UserId
- Username

UserEmail
- UserId
- EmailId
- IsPrimary

Email
- EmailId
- Address

public class Role {
    public int RoleId { get; set; }
    public string Name { get; set; }
    public virtual ICollection<User> Users { get; set; }
}

public class User {
    public int UserId { get; set; }
    public string Username { get; set; }
    public virtual ICollection<Role> Roles { get; set; }
    public virtual ICollection<UserEmail> UserEmails { get; set; }
}

public class UserEmail {
    public int UserId { get; set; }
    public int EmailId { get; set; }
    public bool IsPrimary { get; set; }
    public virtual User User { get; set; }
    public virtual Email Email { get; set; }
}

public class Email {
    public int EmailId { get; set; }
    public string Address { get; set; }
    public virtual ICollection<UserEmail> UserEmails { get; set; }
}

modelBuilder.Entity<Role>().HasKey(q => q.RoleId);

modelBuilder.Entity<Role>()
    .HasMany(q => q.Users)
    .WithMany(q => q.Roles)
    .Map(q => {
                  q.MapLeftKey("RoleId");
                  q.MapRightKey("UserId");
                  q.ToTable("UserRoles");
              });

modelBuilder.Entity<UserEmail>()
    .HasRequired(q => q.User)
    .WithMany(q => q.UserEmails)
    .HasForeignKey(q => q.EmailId);

modelBuilder.Entity（）
.HasRequired（q=>q.User）
.WithMany（q=>q.useremail）
.HasForeignKey（q=>q.EmailId）；

---

是否需要最后一行？

是的，

HasKey

方法与

[Key]

属性具有相同的效果。您可能有很多配置要做，并且更愿意将其全部保存在

ModelBuilder

方法中。另一方面，您可能很少或更喜欢对其中的一些属性使用属性。只是给你一些灵活性

如果你说的是：

.HasForeignKey（q=>q.EmailId）

那么在你的情况下，是的，这是必需的。为什么？因为您已经在
UserEmail
实体中创建了自己的外键属性。如果删除了该属性，则可以删除此行，EF将在名为
Email\u Id
的数据库中为您创建一行。您仍然可以通过导航属性
instanceOfUserEmail.Email.EmailId
访问此文件