实体框架，更新前值的触发机制 [英] Entity Framework, trigger mechanism for before update values

问题描述

在更新对象的值之前，EF中仍然有吗?

Is there anyway in EF to have before update values of object?

例如当说用户对象被保存时，我想知道在更新用户对象值之前用于记录的目的.

e.g. When entity object let's say User is saved, i would like to know for logging purpose before update User object values.

谢谢

推荐答案

如果使用ObjectContext(edmx)，则可以订阅

If you work with ObjectContext (edmx) you can subscribe to the SavingChanges event.

context.SavingChanges += context_SavingChanges;

这可以在执行SaveChanges()时访问原始值和当前值:

This gives access to the original and current values when SaveChanges() is executed:

private void context_SavingChanges (object sender, EventArgs e)
{
    ObjectContext context = sender as ObjectContext;
    if (context != null)
    {
        foreach (ObjectStateEntry entry in context.ObjectStateManager
                                 .GetObjectStateEntries(EntityState.Modified))
        {
            // TODO: do some logging with these values.
            entry.OriginalValues;
            entry.CurrentValues;
        }
    }
}

如果您使用DbContext，则可以通过以下方式进入活动

If you work with DbContext you can get to the event by

((IObjectContextAdapter)this).ObjectContext.SavingChanges

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