嵌套为Linq，带有链接链接列表

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问题描述

我在列表中有一个列表.我只需要列表中的一个值，并且可以使用嵌套的foreach获得我的结果，但我想使用某种linq查询.

我的代码:

var myCity = from c in CountryLists
           select (from city in c.stateList
                   where city.name == passedInValue
                   select city.name).FirstorDefault();

这将Mycity作为某种列表返回，所有值的列表为null 在找到比赛的位置.

我不想浏览城市清单才能找到名称.我如何只有一个价值的置身价值? null或所需的名称?

其他推荐答案

使用SelectMany:

var city = CountryLists
           .SelectMany(x => x.stateList)
           .FirstOrDefault(x => x.name == passedInValue);

其他推荐答案

您可以按照其他指出的方式使用SelectMany(我更喜欢该解决方案)，但是，如果您需要查询语法，则可以使用多个from条款(检查 msdn文档有关更多示例):

var city = (from c in CountryLists
            from city in c.stateList
            where city.name == passedInValue
            select city.name).FirstOrDefault();

它等效于SelectMany方法解决方案，无论如何它在封面下使用它.

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问题描述

I have a List within a list. I only need the one value from the list and can do obtain my result with a nested foreach but I want to use a LINQ query of some sort.

my code:

var myCity = from c in CountryLists
           select (from city in c.stateList
                   where city.name == passedInValue
                   select city.name).FirstorDefault();

This returns myCity as a list of some sort with all values as null EXCEPT for where the match was found.

i don't want to have to walk through the city list to find the name. How can I have only one value in myCity; either null or the desired name?

其他推荐答案

How about using SelectMany:

var city = CountryLists
           .SelectMany(x => x.stateList)
           .FirstOrDefault(x => x.name == passedInValue);

其他推荐答案

You can use SelectMany as other have pointed out (and I prefer that solution myself), however if you'd like the query syntax, you can use multiple from clauses (check the MSDN documentation for more examples):

var city = (from c in CountryLists
            from city in c.stateList
            where city.name == passedInValue
            select city.name).FirstOrDefault();

It is equivalent to the SelectMany method solution, it uses it under the covers anyway.

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