节约更新对象 [英] Update object on saving

问题描述

我有一个实体类（使用模型首先，如果该事项），应该坚持自己的最后一次更改日期。

I have an entity class (using model first, if that matters) that should persist its own last change date.

有没有一种方法来更新这个节约？现在，我只发现覆盖 OnPropertyChanged 但是这是不正确的替代，因为它是在加载对象时，也被称为。

Is there a way to update this on saving? Right now I have only found overriding OnPropertyChanged but that is not the right override, as it is also called when loading the object.

推荐答案

您可以覆盖的SaveChanges您的ObjectContext派生类，只是在保存之前修改的最后更改日期。是这样的：

You can override SaveChanges on your ObjectContext derived class and modify the last change date just before saving. Something like:

public override int SaveChagnes(SaveOptions saveOptions)
{
    var entities = ObjectStateManager.GetObjectStateEntries(EntityState.Modified)
                                     .Where(e => !e.IsRelationship)
                                     .Select(e => e.Entity)
                                     .OfType<YourEntityType>();

    var currentDate = DateTime.Now;
    foreach(var entity in entities)
    {
        entity.LastChangedDate = currentDate;
    }

    return base.SaveChanges(saveOptions);
}

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