从基于另一个列表的列表条件中删除某些元素 [英] Removing certain elements from list condition based on another list

问题描述

我在这里有linq的一个基本问题.尽管这可以通过重复循环来解决.我想知道如何在linq中完成此操作.

I am having a basic issue here with linq . Though this can be solved with repeated loops . I am trying to know how can this be done in linq .

我有两个清单.

List<string> a  = new List<string>{"a","b","c","d","e","f"};
List<string> b = new List<string> { "a", "b", "c", "x", "y", "z" };

我想与列表a和b中的任何元素进行比较.我想从b中删除该元素.换句话说，我想基于列表a中的比较从b中删除{"a"，"b"，"c"}，并且只想在列表b中包含{"x"，"y"，"z"}.是否有一个语句linq可以解决这个问题?

I want to compare with list a and whichever element in b is found in a . I want to remove that element from b . In other words I want to remove {"a","b","c"} from b based on comparison from list a and want to contain only {"x","y","z"} in list b . Is there a single statement linq to solve this ?

推荐答案

(我确定这是几天前另一篇文章的副本，但我找不到它...)

(I'm sure this is a duplicate of another post just a few days ago, but I can't find it...)

如果需要进行修改，可以使用List<T>.RemoveAll:

If you need a modification in place, you can use List<T>.RemoveAll:

b.RemoveAll(x => a.Contains(x));

或更有效的方法(如果列表很大):

Or more efficiently (if the lists are large):

HashSet<string> set = new HashSet<string>(a);
b.RemoveAll(set.Contains);

请注意，在LINQ中就地修改集合并不是惯用的，这就是为什么上面的方法使用特定于.NET 2列表的方法的原因.

Note that modifying a collection in place isn't idiomatic in LINQ, which is why the above uses the .NET 2 list-specific method.

或者，如果您愿意更改b来引用新列表，然后，则可以使用LINQ:

Or if you're happy to change b to refer to a new list instead, then you can use LINQ:

b = b.Except(a).ToList();

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