System.InvalidOperationException:只能以修改后的方式附加实体 [英] System.InvalidOperationException: An entity can only be attached as modified

问题描述

我正在尝试更新名为"Hero"的表，正在使用DataContext，这是代码的样子:-

am trying to update table called "Hero" , am using DataContext , here is how the codes looks like:-

//linq to sql table (automatic generated)
[global::System.Data.Linq.Mapping.TableAttribute(Name="dbo.Hero")]
    public partial class Hero : INotifyPropertyChanging, INotifyPropertyChanged
    {
          //fields methods etc..
    }

还有我自己的局部类英雄...

and there is my own partial class Hero ...

    public partial class Hero : IHero {
           //my fields and methods etc...

            public void Save() {
                using(GameDBDataContext db = new GameDBDataContext()) {
                    db.Heros.Attach(this, true);
                    db.SubmitChanges();
                }
        }
}

但是它抛出了这个:-

System.InvalidOperationException: An entity can only be attached as modified without original state if it declares a version member or does not have an update check policy.

该问题的解决方案是什么?

what is the solution for this problem?

我已经尝试过了:-

public void Save() {
    using(GameDBDataContext db = new GameDBDataContext()) {
        db.Heros.Attach(this, db.Heros.SingleOrDefault(x => x.id == EntityID));
    }
}

并抛出:-System.NotSupportedException: An attempt has been made to Attach or Add an entity that is not new, perhaps having been loaded from another DataContext. This is not supported.

推荐答案

我认为您没有正确使用Attach方法.您是否看过 http://msdn.microsoft.com/en-us/library/bb548978.aspx 吗?

I don't think you're using the Attach method correctly. Have you looked at this http://msdn.microsoft.com/en-us/library/bb548978.aspx ?

如果您要传递的对象是用代码创建的(而不是通过反序列化)，则可能无法使用.如果它是通过反序列化完成的，那么我建议您尝试制作原始对象的副本，对其进行修改，并使用接受修改后的实体和未修改的实体Attach(Entity old, Entity new)的重载.

If the object you're passing in was created in code (rather than through deserialization) it probably won't work. If it was made via deserialization then I would recommend you try making a copy of the original object, modifying it, and using the overload which accepts a modified and unmodified entity Attach(Entity old, Entity new).

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