我最近一直在尝试使用 ef core,但是 ef core 中的多对多关系有些令人困惑。
public class Location
{
public Guid Id { get; set; }
public ICollection<LocationInstructor> LocationInstructors { get; set; } = new List<LocationInstructor>();
}
public class Instructor
{
public Guid Id { get; set; }
public ICollection<LocationInstructor> LocationInstructors { get; set; } = new List<LocationInstructor>();
}
public class LocationInstructor
{
public Guid LocationId { get; set; }
public Location Location { get; set; }
public Guid InstructorId { get; set; }
public Instructor Instructor { get; set; }
}
并在 dbcontext
protected override void OnModelCreating(ModelBuilder modelBuilder)
{
base.OnModelCreating(modelBuilder);
modelBuilder.Entity<LocationInstructor>()
.HasKey(bc => new { bc.LocationId, bc.InstructorId });
modelBuilder.Entity<LocationInstructor>()
.HasOne(bc => bc.Location)
.WithMany(b => b.LocationInstructors)
.HasForeignKey(bc => bc.InstructorId);
modelBuilder.Entity<LocationInstructor>()
.HasOne(bc => bc.Instructor)
.WithMany(c => c.LocationInstructors)
.HasForeignKey(bc => bc.LocationId);
}
这是我尝试执行的操作
var instructors = new List<Instructor>
{
new Instructor(),new Instructor()
};
await applicationDbContext.Instructors.AddRangeAsync(instructors);
Location location = new Location();
foreach (var instructor in instructors)
{
location.LocationInstructors.Add(new LocationInstructor { Instructor= instructor, Location=location});
}
await applicationDbContext.Locations.AddAsync(location);
await applicationDbContext.SaveChangesAsync();
当我运行这个操作时,我可以看到下面的截图
所以,我的问题是为什么 2 值不同?我在这里错过了什么吗?
最佳答案
你搞砸了关系映射,基本上是关联 InstructorId
与 Location
和 LocationId
与 Instructor
:
modelBuilder.Entity<LocationInstructor>()
.HasOne(bc => bc.Location) // (1)
.WithMany(b => b.LocationInstructors)
.HasForeignKey(bc => bc.InstructorId); // (1)
modelBuilder.Entity<LocationInstructor>()
.HasOne(bc => bc.Instructor) // (2)
.WithMany(c => c.LocationInstructors)
.HasForeignKey(bc => bc.LocationId); // (2)
当然,它们应该配对 (
LocationId
, Location
) 和 ( InstructorId
, Instructor
)modelBuilder.Entity<LocationInstructor>()
.HasOne(bc => bc.Location) // (1)
.WithMany(b => b.LocationInstructors)
.HasForeignKey(bc => bc.LocationId); // (1)
modelBuilder.Entity<LocationInstructor>()
.HasOne(bc => bc.Instructor) // (2)
.WithMany(c => c.LocationInstructors)
.HasForeignKey(bc => bc.InstructorId); // (2)
其中 btw 是默认的常规映射,因此可以跳过这些(约定优于配置)。
关于entity-framework - ef core - 多对多关系,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/61543438/