繼續配置實體之間的第三種關係,即一對一的關係。
以考研報名爲例,一個人有唯一的身份證號,在首次報名時會生成一個唯一的考試號,這樣身份證號和考試號就是一對一的關係。
同樣提供ER圖如下:
Person類:
public class Person
{
public string PersonIdentityNum { get; set; }
public string PersonName { get; set; }
public virtual Exam Exam { get; set; }
}
Exam類:
public class Exam
{
public string ExamNo { get; set; }
public decimal ExamScore1 { get; set; }
public decimal ExamScore2 { get; set; }
public decimal ExamScore3 { get; set; }
public decimal ExamScore4 { get; set; }
public string PersonIdentityNum { get; set; }
public virtual Person Person { get; set; }
}
然後在數據庫上下文中配置一對一的關係:
public class MyDbContext : DbContext
{
public MyDbContext()
{
}
public MyDbContext(DbContextOptions<MyDbContext> options)
: base(options)
{
}
protected override void OnModelCreating(ModelBuilder modelBuilder)
{
base.OnModelCreating(modelBuilder);
//指定主鍵
modelBuilder.Entity<Person>().ToTable("Person").HasKey(o => o.PersonIdentityNum);
modelBuilder.Entity<Exam>().ToTable("Exam").HasKey(o => o.ExamNo);
//一個人對應一個考生
modelBuilder.Entity<Person>()
.HasOne(o => o.Exam)
.WithOne(o => o.Person).HasForeignKey<Exam>(o => o.PersonIdentityNum);
}
protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
{
base.OnConfiguring(optionsBuilder);
optionsBuilder.UseSqlServer("server=xxx.xxx.xxx.xxx;database=數據庫名;uid=數據庫賬號;pwd=數據庫賬號密碼;");
}
public DbSet<Person> Person { get; set; }
public DbSet<Exam> Exam { get; set; }
}
最後就可以直接關聯查詢:
using (var db = new ChipContext())
{
//查詢姓名爲張三的考試信息
Exam exam = db.Person.Include(o => o.Exam).FirstOrDefault(o => o.PersonName.Equals("張三")).Exam;
}