实体框架:SaveChanges()一种方式工作,另一种方式不工作。为什么?[已关闭]

如果我这样做,上下文。SaveChanges()工作正常:

List<Messages> DbChangedMessages = context.Messages
                    .Where(m => m.Status == 0)
                    .OrderBy(m => m.insertdate)
                    .Take(maxNumberOfMessages)
                    .ToList();

//look for messages that point to invalid template
List<Messages> invalidMessages = (from m in DbChangedMessages
                                 join t in context.Templates on m.templateId equals t.id
                                 where m.Status == 0 && t.invalid == true
                                 select m)
                                 .ToList();

if (invalidMessages.Count > 0)
{
    //set Status=11 for all messages that have Status=0 and point to an invalid template
    invalidMessages.ForEach(m => m.Status = 11);
    context.SaveChanges();
}

新状态11写入数据库。 但是,如果我将第一个查询移动到一个静态函数,返回这样的列表,SaveChanges()将不起作用(其余的保持不变)。

List<Messages> DbChangedMessages = MessageMethods.GetChangedMessages(maxNumberOfMessages);

//look for messages that point to invalid template
List<Messages> invalidMessages = (from m in DbChangedMessages
                                 join t in context.Templates on m.templateId equals t.id
                                 where m.Status == 0 && t.invalid == true
                                 select m)
                                 .ToList();

if (invalidMessages.Count > 0)
{
    //set Status=11 for all messages that have Status=0 and point to an invalid template
    invalidMessages.ForEach(m => m.Status = 11);
    context.SaveChanges();
}

为什么?