从列表中查找另一个列表中存在的项目 [英] Find items from a list which exist in another list

问题描述

我有一个List<PropA>

PropA  
{  
    int a;  
    int b;  
}

和另一个List<PropX>

PropX  
{  
    int a;  
    int b;  
}

现在，我必须使用lambda或LINQ从List<PropX>中找到与 b 属性匹配的List<PropA>中存在的项目.

Now i have to find items from List<PropX> which exist in List<PropA> matching b property using lambda or LINQ.

推荐答案

您要做的是Join这两个序列. LINQ有一个Join运算符可以做到这一点:

What you want to do is Join the two sequences. LINQ has a Join operator that does exactly that:

List<PropX> first;
List<PropA> second;

var query = from firstItem in first
    join secondItem in second
    on firstItem.b equals secondItem.b
    select firstItem;

请注意，LINQ中的Join运算符也被编写为比朴素的实现要高效得多，该朴素的实现将对每个项目的第二个集合进行线性搜索.

Note that the Join operator in LINQ is also written to perform this operation quite a bit more efficiently than the naive implementations that would do a linear search through the second collection for each item.

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