EF：在DbContext上禁用“AutoDetectChangesEnabled”和“ProxyCreationEnabled”时，从多对多关系创建/删除关系 [英] EF: Create/Remove relation from Many-to-Many relations when `AutoDetectChangesEnabled` and `ProxyCreationEnabled` are disabled on DbContext

问题描述

1. 已知 Foo.Id 和 Bar.Id 我如何创建他们的关系而不从DB加载实体。

1. Knowning Foo.Id and Bar.Id how can I create their relation without loading the entities from the DB.

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; }
}

此配置在 DbContext 构造函数：

Also this configuration are disabled in DbContext constructor:

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

是否可以删除关系？

And how it is possible to remove the relationship?

---

示例：

---

Example:

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定义关系。

How can I define relation here, without changing the configuration.

提前谢谢。

推荐答案

解决方案，这里是帮助方法：

Ok, have found the solution and here is the helper method:

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
        );
}

在我的示例中使用它从问题：

And using it in my example from the question:

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();
}

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