在EF Core 5中保存相关数据(多对多)，而不获取实际记录

// 定义实体类
public class A
{
    public int Id { get; set; }
    public string Name { get; set; }
    public ICollection<AB> ABs { get; set; }
}

public class B
{
    public int Id { get; set; }
    public string Name { get; set; }
    public ICollection<AB> ABs { get; set; }
}

public class AB
{
    public int AId { get; set; }
    public A A { get; set; }
    public int BId { get; set; }
    public B B { get; set; }
}

// 配置关系
public class ABConfiguration : IEntityTypeConfiguration<AB>
{
    public void Configure(EntityTypeBuilder<AB> builder)
    {
        builder.HasKey(ab => new { ab.AId, ab.BId });

        builder.HasOne(ab => ab.A)
            .WithMany(a => a.ABs)
            .HasForeignKey(ab => ab.AId);

        builder.HasOne(ab => ab.B)
            .WithMany(b => b.ABs)
            .HasForeignKey(ab => ab.BId);
    }
}

// 添加数据
var a1 = new A { Name = "A1" };
var a2 = new A { Name = "A2" };
var b1 = new B { Name = "B1" };
var b2 = new B { Name = "B2" };

var ab1 = new AB { A = a1, B = b1 };
var ab2 = new AB { A = a2, B = b1 };
var ab3 = new AB { A = a2, B = b2 };

// 保存数据
using (var context = new YourDbContext())
{
    context.A.Add(a1);
    context.A.Add(a2);
    context.B.Add(b1);
    context.B.Add(b2);
    context.AB.Add(ab1);
    context.AB.Add(ab2);
    context.AB.Add(ab3);

    context.SaveChanges();
}