如何展平字典< string，List< string>>在linq中并保留结果中的关键 [英] How to flatten a dictionary<string,List<string>> in linq and keep the key in the results

问题描述

如何在linq中实现以下目标?我觉得应该有一个Linq替代方案.

How do you achieve the following in linq? I feel there should be a Linq alternative.

    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

推荐答案

您可以使用 SelectMany 扩展方法:

You can use SelectMany extension method:

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

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