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entity-framework - ef core - 多对多关系

问题描述

我最近一直在尝试使用 ef core，但是在 ef core 中的多对多关系中有些东西令人困惑。

    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 在此处输入图像描述

所以，我的问题是为什么 2 值不同？我在这里错过了什么吗？

标签： entity-frameworkasp.net-core.net-coreentity-framework-core

解决方案

你搞砸了关系映射，基本上InstructorId与Location和相关LocationId联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，它们应该是配对的 ( 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)

顺便说一句，这是默认的常规映射，因此可以跳过这些（约定优于配置）。

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