.NetFramwork下EntityFramework Codefirst用例

2024-02-16 18:38:16

``#### Codefirst

创建Model文件夹
Model文件夹下创建两个类（你随意，想怎么写就怎么写）

public class Grade
    {
        [Required]
        public int GradeId { get; set; }
        public string GradeName { get; set; }
        public string Section { get; set; }
        public List<Student> Students { get; set; }
    }

public class Student
    {
        [Required]
        public int StudentID { get; set; }
        [StringLength(maximumLength:50),Column(TypeName ="nvarchar")]
        public string StudentName { get; set; }
        public DateTime? DateOfBirth { get; set; }
        public byte[] Photo { get; set; }
        public decimal Height { get; set; }

        [ForeignKey(nameof(Grade))]
        public int GradeID { get; set; }
        public Grade Grade { get; set; }
    }

创建一个上下文类

public class SchoolContext : DbContext
    {
        //构造函数
        public SchoolContext() : base(nameOrConnectionString: "SchoolContext")//绑定app.config文件的链接字符串
        {
            Database.SetInitializer<SchoolContext>(strategy: null);//CodeFirst 上下文的默认策略是 System.Data.Entity.CreateDatabaseIfNotExists 的实例。
        }
        protected override void OnModelCreating(DbModelBuilder modelBuilder)
        {
            base.OnModelCreating(modelBuilder);
            modelBuilder.Conventions.Remove<OneToManyCascadeDeleteConvention>();
            modelBuilder.Conventions.Remove<ManyToManyCascadeDeleteConvention>();
        }
        public DbSet<Student> Students { get; set; }
        public DbSet<Grade> Grades { get; set; }
    }