如何从一个列表中删除另一个列表中的所有项目? [英] How to remove from one list all the items in another?

问题描述

我正在从远程数据库中读取一组行，并从本地数据库中读取一组类似的行，然后使用RemoveAll摆脱本地已经存在的远程行...

I'm reading a set of rows from a remote database, and a similar set from a local database, and then using RemoveAll to get rid of remote rows that are already present locally...

remote_events = (From a In remote.Events
                          Where ...etc...).ToList
local_events = (From a In local.Events
                            Where ...etc...).ToList
remote_events.RemoveAll(Function (ByVal event_row As Remote_Event)
    (From a In local_events Where a.Identifier = event_row.Identifier).Count > 0)

但这对我来说似乎不正确.当我真正需要做的只是检查是否存在匹配项时，我认为我不应该在计算任何事情.我已经尝试了IsDBNull和IsNothing的各种用法，但是胡说八道.我无法使用.Except(如建议的此处)，因为列表元素不是同一类型.

but this doesn't seem right to me. I don't think I should be counting things when all I really need to do is check whether a match exists. I've tried various usages of IsDBNull and IsNothing but get nonsense. I can't use .Except (as suggested here) because the list elements are not the same type.

有更好的方法吗?

推荐答案

一种方法是

    remote_events.RemoveAll(Function(e) local_events.Exists(Function(f) f.Identifier = e.Identifier))

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