实体框架代码首先使用外键作为复合主键的一部分

public class EntityA
{
    [Key]
    public int Id { get; set; }

    [Key]
    [ForeignKey("EntityB")]
    public int EntityBId { get; set; }

    public EntityB EntityB { get; set; }
}

public class EntityB
{
    [Key]
    public int Id { get; set; }

    public ICollection<EntityA> EntityAs { get; set; }
}

public class EntityAConfiguration : EntityTypeConfiguration<EntityA>
{
    public EntityAConfiguration()
    {
        HasKey(e => new { e.Id, e.EntityBId });

        HasRequired(e => e.EntityB)
            .WithMany(b => b.EntityAs)
            .HasForeignKey(e => e.EntityBId);
    }
}

public class EntityBConfiguration : EntityTypeConfiguration<EntityB>
{
    public EntityBConfiguration()
    {
        HasKey(e => e.Id);
    }
}

public class MyDbContext : DbContext
{
    protected override void OnModelCreating(DbModelBuilder modelBuilder)
    {
        modelBuilder.Configurations.Add(new EntityAConfiguration());
        modelBuilder.Configurations.Add(new EntityBConfiguration());
    }
}