如何在 linq 中展平字典<string,List<string>> 并在结果中保留键

Posted 2023-02-23

【中文标题】如何在 linq 中展平字典<string,List<string>> 并在结果中保留键

【英文标题】：How to flatten a dictionary<string,List<string>> in linq and keep the key in the results

【发布时间】：2016-04-27 22:15:41

【问题描述】：

你如何在 linq 中实现以下目标？我觉得应该有一个 Linq 替代方案。

    var foods = new Dictionary<string, List<string>>();
    foods.Add("Cake", new List<string>()  "Sponge", "Gateux", "Tart" );
    foods.Add("Pie", new List<string>()  "Mud", "Apple" );
    foods.Add("Roll", new List<string>()  "Sausage" );

    var result = new List<Tuple<string, string>>();
    foreach (var food in foods)
    
        foreach (var detail in food.Value)
        
            result.Add(new Tuple<string, string>(food.Key, detail));
        
    

ie
cake <sponge, gateux>
pie <apple>

to

cake, sponge
cake, gateux
pie,  apple

谢谢

【参考方案1】：

你可以使用SelectMany扩展方法：

var result= foods.SelectMany(f=>f.Value.Select(s=>new Tuple<string, string>(f.Key, s)))
                 .ToList();

【参考方案2】：

 var result = (from food in foods 
               from detail in food.Value 
               select new Tuple<string, string>(food.Key, detail)).ToList();

【参考方案3】：

Linq 是一个查询。这就是“q”的含义。您正在将项目添加到字典中。试试这个

            Dictionary<string, List<string>> foods = new Dictionary<string, List<string>>()   
               "cake",  new List<string>() "Sponge", "Gateux", "Tart",
               "Pie",  new List<string>() "Mud", "Apple",
               "Roll",  new List<string>() "Sausage",
            ;