EntityFramework：FluentAPI关系映射

1.表的设计

2.关系映射的方法

基本套路 this.Has***(x=>x.aaa).with***() 当前这个表的和aaa 属性的表的关系是has定义，with定义的是aaa表和这个表的关系

HasOptional() 有一个可以选（可以为空）

HasRequired() 有一个必须选（不能为空）

HasMany()  有很多的

WithOptional() 可选的

WithRequired() 必须的

WithMany() 很多的

3.创建一个DbContext类

public class FluentAPIContext : DbContext
    {
        public FluentAPIContext() : base("name=Conn") { }

        public virtual DbSet<User> User { get; set; }
        public virtual DbSet<Role> Role { get; set; }
        public virtual DbSet<Action> Action { get; set; }
        public virtual DbSet<UserAction> UserAction { get; set; }


        protected override void OnModelCreating(DbModelBuilder modelBuilder)
        {
            base.OnModelCreating(modelBuilder);

            modelBuilder.Configurations.AddFromAssembly(Assembly.GetExecutingAssembly());
        }
    }

4.Model 类

    public class User
    {
        public int Id { get; set; }
        public string Name { get; set; }

        public virtual ICollection<Role> Roles { get; set; } = new List<Role>();
        public virtual ICollection<UserAction> UserActions { get; set; } = new List<UserAction>();
    }

    public class Role
    {
        public int Id { get; set; }
        public string Name { get; set; }
        public virtual ICollection<User> Users { get; set; } = new List<User>();
    }

    public class Action
    {
        public int Id { get; set; }
        public string Name { get; set; }
    }

    public class UserAction
    {
        public int Id { get; set; }
        public int UserId { get; set; }
        public virtual User User { get; set; }
        public int ActionId { get; set; }
        public virtual Action Action { get; set; }
        public bool HasPermisssin { get; set; }
    }

5.配置类

    public class UserMap : EntityTypeConfiguration<User>
    {
         public UserMap()
        {
            this.ToTable("sys_user");
            //多对多
            this.HasMany(x => x.Roles).WithMany().Map(x => x.ToTable("sys_user_role").MapLeftKey("UserId").MapRightKey("RoleId"));
            //双向设置，一般不介意这样设置，一般一对多只要设置多的一方,或者说这里不用设置。
            this.HasMany(x => x.UserActions).WithRequired().HasForeignKey(x => x.UserId);
        }
    }

    public class RoleMap : EntityTypeConfiguration<Role>
    {
         public RoleMap()
        {
            this.ToTable("sys_role");
        }
    }

        public UserActionMap()
        {
            this.ToTable("sys_user_action");
            //一对多
            this.HasRequired(x => x.User).WithMany().HasForeignKey(x => x.UserId);
            this.HasRequired(x => x.Action).WithMany().HasForeignKey(x => x.ActionId);
        }

6.测试代码

class Program
    {
        static void Main(string[] args)
        {
            using (FluentAPIContext ctx = new FluentAPIContext())
            {
                //User user = new User();
                //user.Name = "admin2";
                //ctx.User.Add(user);
                //Action action = new Action();
                //action.Name = "修改";
                //ctx.Action.Add(action);
                //UserAction userAction = new UserAction();
                //userAction.User = user;
                //userAction.Action = action;
                //userAction.HasPermisssin = false;
                //ctx.UserAction.Add(userAction);
                //ctx.SaveChanges();

                //User user = ctx.User.First();
                //foreach (UserAction userAction in user.UserActions)
                //{
                //    Console.WriteLine(userAction.HasPermisssin);
                //}

                User u1 = new User();
                u1.Name = "admin";
                User u2 = new User();
                u1.Name = "ordinary";
                Role r1 = new Role();
                r1.Name = "管理员";
                Role r2 = new Role();
                r2.Name = "普通会员";

                u1.Roles.Add(r1);
                u2.Roles.Add(r2);
                ctx.User.Add(u1);
                ctx.User.Add(u2);
                ctx.SaveChanges();

            }
        }
    }

7.一对多关系配置简单例子

 this.HasRequired(x => x.User).WithMany().HasForeignKey(x => x.UserId);

8.多对多关系配置简单例子

  this.HasMany(x => x.Roles).WithMany().Map(x => x.ToTable("sys_user_role").MapLeftKey("UserId").MapRightKey("RoleId"));