如何获得一个不在另一个列表中的项目列表 [英] How to Attain a list of items of items not on another list

问题描述

我想从名称不在第二个列表中的列表中获取BeerNames的列表.

I want to attain a list of BeerNames from a list whose names are not on a second list.

var myList=(from f in Beers where ...
              select f.BeerNames).ToList

var storeList(from f in Store where...
                select f).ToList()

MyList将具有一些不在StoreList上的BeerName.我如何找到那些BeerName?我尝试了.Except和!Contains，但是我意识到我做错了事，并且缺少一些关键知识. 谢谢

MyList will have some BeerNames that are not on StoreList. How do I find those BeerNames? I tried .Except and !Contains but I realize I'm doing something wrong, and missing some key bit of knowledge. thanks

如果我更改

var storeList(from f in Store where...
                select f).ToList()

到

var storeList(from f in Store where...
                select f.BeerNames).ToList()

然后我可以使用除List1.Except(List2)之类的东西.我不确定是否有更好的方法.抱歉，如果不清楚，我正在尝试:)

then I can use except such as List1.Except(List2). I wasn't sure if there was a better way. Sorry folks if this isn't clear...I'm trying:)

推荐答案

var list1 = new String[] {"ABC1","ABC2", "ABC3", "ABC4"} ;
var list2 = new String[] {"ABC3","ABC4", "ABC5", "ABC6"} ;
var list3 = list1.Except(list2); // list3 holds ABC1, ABC2

除了工作正常之外.

我怀疑是linq查询返回的项目中有问题. 似乎像第一个中的f.BeerNames和StoreList中的f都没有指向相同的数据类型.

I suspect issue is in the item returned from the linq query. Seems like f.BeerNames in first, and f in StoreList are not pointing to same datatype.

对于异构类型

var list1 = from s in new String[] {"ABC1","ABC2", "ABC3", "ABC4"} select new {BeerName=s,Id = Guid.NewGuid().ToString()}  ;
var list2 = new String[] {"ABC3","ABC4", "ABC5", "ABC6"} ;
var intermediateList = list1.Select(i=>i.BeerName).Except(list2);
var list3 = from l1 in list1
        join l2 in intermediateList on l1.BeerName equals l2
        select l1;


list1.Dump(); // run in linqPad
intermediateList.Dump();// run in linqPad
list3.Dump();// run in linqPad

list3返回以下内容

list3 returns following

啤酒名称ID

ABC1 569ace9a-66c4-46aa-bbf5-50d586a2886f

ABC1 569ace9a-66c4-46aa-bbf5-50d586a2886f

ABC2 af456094-9692-4771-b489-8b3cca8aa938

ABC2 af456094-9692-4771-b489-8b3cca8aa938

使用 LinqPad 来运行上述命令，或删除.Dump()以在VS中执行.

Use LinqPad to run the above, or remove .Dump() to execute in VS.

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