将Update Linq上的列排除到实体

Question

我正在尝试为所有记录存储更新日期和创建日期。

我添加Override for SaveChanges方法更新记录时的问题CreatedDate变为null。所以我的问题是，在更新时如何保持CreatedDate不做任何更改。

    public override int SaveChanges()
    {
        try
        {
            var changeSet = ChangeTracker.Entries();
            dynamic obj;
            if (changeSet != null)
            {
                foreach (var entry in changeSet.Where(c => c.State == EntityState.Added))
                {
                    obj = entry.Entity;
                    obj.CreatedDate = DateTime.UtcNow;
                }
                foreach (var entry in changeSet.Where(c => c.State == EntityState.Modified))
                {
                    obj = entry.Entity;
                    obj.ModifiedDate = DateTime.UtcNow;
                }
            }
        }
        catch (Exception ex)
        {
            throw;
        }
        return base.SaveChanges();
    }

Answer 1

简单，更新时不要传递CreateDate！

 if (changeSet != null)
            {
                foreach (var entry in changeSet.Where(c => c.State == EntityState.Added))
                {
                    obj = entry.Entity;

                }
                foreach (var entry in changeSet.Where(c => c.State == EntityState.Modified))
                {
                    obj = entry.Entity;

                }
            }