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;
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。
最佳答案
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();
}
关于c# - EF : Create/Remove relation from Many-to-Many relations when `AutoDetectChangesEnabled` and `ProxyCreationEnabled` are disabled on DbContext,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/39708439/