实体：
public virtual DbSet StuInfo { get; set; }
public class StuInfo { [Key]//主键 public int Sid { get; set; } public string Name { get; set; } public DateTime? BirthDay { get; set; } = null;//？代表可以为空，=null默认值为空 public virtual ICollection Scores { get; set; } = new HashSet(); //和表建立外键关系 }
[ForeignKey("StuInfoId")]外键
