csharp EF6 - 多对多第二种方式

Posted 2021-05-12

namespace EntityFramework.Entity
{
    public class BaseEntity
    {
        public int Id { get; set; }
        public DateTime CreatedTime { get; set; }
        public DateTime ModifiedTime { get; set; }
    }
    
    public class Student : BaseEntity
    {
        public string Name { get; set; }
        public byte Age { get; set; }
        public virtual ICollection<StudentCourse> StudentCourses { get; set; }
    }
	
    public class Course : BaseEntity
    {
        public string Name { get; set; }
        public int MaximumStrength { get; set; }
        public virtual ICollection<StudentCourse> StudentCourses { get; set; }
    }

    public class StudentCourse : BaseEntity
    {
        public int StudentId { get; set; }
        public virtual Student Student { get; set; }

        public int CourseId { get; set; }
        public virtual  Course Course { get; set; }
    }
}

namespace EntityFramework.Map
{
    public class StudentMap : EntityTypeConfiguration<Student>
    {
        public StudentMap()
        {
            // table
            ToTable("Students");

            // key
            HasKey(t => t.Id);

            // fields
            Property(x => x.Id).HasDatabaseGeneratedOption(DatabaseGeneratedOption.Identity);

            // relationship
            HasMany(m => m.StudentCourses)
                .WithRequired(o => o.Student)
                .HasForeignKey(k => k.StudentId);
        }
    }
	
    public class CourseMap : EntityTypeConfiguration<Course>
    {
        public CourseMap()
        {
            // table
            ToTable("Courses");

            // key
            HasKey(k => k.Id);

            // relationship
            HasMany(m => m.StudentCourses)
                .WithRequired(o => o.Course)
                .HasForeignKey(k => k.CourseId);
        }
    }
}

namespace EntityFramework
{
    public class EfDbContext : DbContext
    {
        public EfDbContext() : base("name=ConnectionString")
        {
            Database.SetInitializer(new CreateDatabaseIfNotExists<EfDbContext>());
        }

        public DbSet<Student> Students { get; set; }
        public DbSet<Course> Courses { get; set; }
        public DbSet<StudentCourse> StudentCourses { get; set; }

        protected override void OnModelCreating(DbModelBuilder modelBuilder)
        {
            var typesToRegister = Assembly.GetExecutingAssembly().GetTypes()
                .Where(type => !string.IsNullOrEmpty(type.Namespace))
                .Where(type => type.BaseType != null && type.BaseType.IsGenericType
                                                     && type.BaseType.GetGenericTypeDefinition() ==
                                                     typeof(EntityTypeConfiguration<>));

            foreach (var type in typesToRegister)
            {
                dynamic configurationInstance = Activator.CreateInstance(type);
                modelBuilder.Configurations.Add(configurationInstance);
            }

            base.OnModelCreating(modelBuilder);
        }
    }
	
    class Program
    {
        static void Main(string[] args)
        {
            using (var ctx = new EfDbContext())
            {
                ctx.Database.Log = Console.WriteLine;

                var student = new Student
                {
                    Name = "Jeffcky",
                    Age = 26,
                    CreatedTime = DateTime.Now,
                    ModifiedTime = DateTime.Now
                };
                var course1 = new Course
                {
                    Name = "C#",
                    MaximumStrength = 12,
                    CreatedTime = DateTime.Now,
                    ModifiedTime = DateTime.Now
                };
                var course2 = new Course
                {
                    Name = "EntityFramework 6.x",
                    MaximumStrength = 12,
                    CreatedTime = DateTime.Now,
                    ModifiedTime = DateTime.Now
                };

                var studentCourse1 = new StudentCourse
                {
                    Student = student,
                    Course = course1,
                    CreatedTime = DateTime.Now,
                    ModifiedTime = DateTime.Now
                };
                var studentCourse2 = new StudentCourse
                {
                    Student = student,
                    Course = course2,
                    CreatedTime = DateTime.Now,
                    ModifiedTime = DateTime.Now
                };

                ctx.StudentCourses.Add(studentCourse1);
                ctx.StudentCourses.Add(studentCourse2);
                ctx.SaveChanges();
            }
            Console.ReadKey();
        }
    }
}