如何从ChangeTracker获取原始实体

问题描述

是否可以从ChangeTracker获取原始实体本身(而不仅仅是原始值)?

Is there a way to get the original Entity itself from the ChangeTracker (rather than just the original values)?

如果State是Modified，那么我想我可以这样做:

If the State is Modified, then I suppose I could do this:

// Get the DbEntityEntry from the DbContext.ChangeTracker...

// Store the current values
var currentValues = entry.CurrentValues.Clone();

// Set to the original values
entry.CurrentValues.SetValues(entry.OriginalValues.Clone());

// Now we have the original entity
Foo entity = (Foo)entry.Entity;

// Do something with it...

// Restore the current values
entry.CurrentValues.SetValues(currentValues);

但这似乎不太好，我敢肯定我不知道有问题...有更好的方法吗?

But this doesn't seem very nice, and I'm sure there are problems with it that I don't know about... Is there a better way?

我正在使用Entity Framework 6.

I'm using Entity Framework 6.

推荐答案

覆盖DbContext的SaveChanges或仅从上下文访问ChangeTracker:

Override SaveChanges of DbContext or just access ChangeTracker from the context:

foreach (var entry in context.ChangeTracker.Entries<Foo>())
{
    if (entry.State == System.Data.EntityState.Modified)
    {
        // use entry.OriginalValues
        Foo originalFoo = CreateWithValues<Foo>(entry.OriginalValues);
    }
}

---

这是一种将使用原始值创建新实体的方法.因此，所有实体都应具有无参数的公共构造函数，您可以简单地使用new:

private T CreateWithValues<T>(DbPropertyValues values)
    where T : new()
{
    T entity = new T();
    Type type = typeof(T);

    foreach (var name in values.PropertyNames)
    {
        var property = type.GetProperty(name);
        property.SetValue(entity, values.GetValue<object>(name));
    }

    return entity;
}

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