c# - EF : Create/Remove relation from Many-to-Many relations when `AutoDetectChangesEnabled` and `ProxyCreationEnabled` are disabled on DbContext

Question

1. 知道 Foo.Id 和 Bar.Id 我如何在不从数据库加载实体的情况下创建它们的关系。

   class Foo {
       public int Id { get; set; }
       public Lst<Bar> Bars { get; set; }
   }
   
   class Bar {
       public int Id { get; set; }
       public Lst<Foo> Foos { get; set; }
   }
   

   此外，此配置在 DbContext 构造函数中被禁用:

   Configuration.AutoDetectChangesEnabled = false;
   Configuration.ProxyCreationEnabled = false;
   Configuration.LazyLoadingEnabled = false;
   

2. 如何解除关系？

---

例子:

using (var ctx = new DbCtx())
{
    ctx.Configuration.LazyLoadingEnabled = false;
    ctx.Configuration.ProxyCreationEnabled = false;
    ctx.Configuration.AutoDetectChangesEnabled = false;
    ctx.Database.Log += Console.WriteLine;

    var foo = new Foo {Id = 1, Bars = new List<Bar>() };
    var bar = new Bar { Id = 3, Foos = new List<Foo>() };

    // This approach wont work, as AutoDetectChanges are disabled
    ctx.Foos.Attach(foo);
    ctx.Bars.Attach(bar);

    foo.Bars.Add(bar);
    ctx.SaveChanges();
}

如何在不更改配置的情况下在这里定义关系。

提前谢谢你。

Answer 1

好的，已经找到解决方案，这里是辅助方法:

static void ChangeRelationship<T1, T2>(
    IObjectContextAdapter ctx, 
    T1 a, 
    T2 b, 
    Expression<Func<T1, object>> getNavigationProperty,
    EntityState state) where T1: class
{
    ctx
        .ObjectContext
        .ObjectStateManager
        .ChangeRelationshipState(
            a,
            b,
            getNavigationProperty,
            state
        );
}

并在问题示例中使用它:

using (var ctx = new DbCtx())
{
    ctx.Configuration.LazyLoadingEnabled = false;
    ctx.Configuration.ProxyCreationEnabled = false;
    ctx.Configuration.AutoDetectChangesEnabled = false;
    ctx.Database.Log += Console.WriteLine;

    var foo = new Foo {Id = 1, Bars = new List<Bar>()};
    var bar = new Bar { Id = 3, Foos = new List<Foo>() };

    ctx.Entry(foo).State = EntityState.Unchanged;
    ctx.Entry(bar).State = EntityState.Unchanged;

    // create
    ChangeRelationship(ctx, foo, bar, x => x.Bars, EntityState.Added);
    ctx.SaveChanges();

    // remove
    ChangeRelationship(ctx, foo, bar, x => x.Bars, EntityState.Deleted);
    ctx.SaveChanges();
}