c# - C# 字典中的 LINQ 选择

Question

我在 C# 中有下一本字典

Dictionary<string, object> subDictioanry = new Dictionary<string, object>();

List<Dictionary<string, string>> subList = new List<Dictionary<string, string>>();

subList.Add(new Dictionary<string, string>(){
    {"valueLink", "link1"},
    {"valueTitle","title1"}
});
subList.Add(new Dictionary<string, string>(){
    {"valueLink", "link2"},
    {"valueTitle","title2"}
});
subList.Add(new Dictionary<string, string>(){
    {"valueLink", "link3"},
    {"valueTitle","title3"}
});

subDictioanry.Add("title", "title");
subDictioanry.Add("name", "name");
subDictioanry.Add("fieldname1", subList);

Dictionary<string, object> exitDictionary = new Dictionary<string, object>();
exitDictionary.Add("first", subDictioanry);
exitDictionary.Add("second", subDictioanry);

是否有可能在 LINQ 选择的帮助下获得所有“valueTitle”？

更新：对不起，我应该先写 - 我需要从 exitDictionary 中获取结果，而不是从 subList

Answer 1

如果您按fieldname1值搜索，请尝试以下操作：

var r = exitDictionary
   .Select(i => i.Value).Cast<Dictionary<string, object>>()
   .Where(d => d.ContainsKey("fieldname1"))
   .Select(d => d["fieldname1"]).Cast<List<Dictionary<string, string>>>()
   .SelectMany(d1 => 
       d1
        .Where(d => d.ContainsKey("valueTitle"))
        .Select(d => d["valueTitle"])
        .Where(v => v != null)).ToList();

如果您正在查看subDictionary(Dictionary<string, object>显式) 中的值的类型，您可以这样做：

var r = exitDictionary
   .Select(i => i.Value).Cast<Dictionary<string, object>>()
   .SelectMany(d=>d.Values)
   .OfType<List<Dictionary<string, string>>>()
   .SelectMany(d1 => 
       d1
        .Where(d => d.ContainsKey("valueTitle"))
        .Select(d => d["valueTitle"])
        .Where(v => v != null)).ToList();

两种选择都将返回：

title1
title2
title3
title1
title2
title3

Answer 2

一种方法是首先用 a 展平列表SelectMany：

subList.SelectMany(m => m).Where(k => k.Key.Equals("valueTitle"));

Answer 3

这将返回与您的键匹配的所有值valueTitle

subList.SelectMany(m => m).Where(kvp => kvp.Key == "valueTitle").Select(k => k.Value).ToList();

Answer 4

var res = exitDictionary
            .Select(p => p.Value).Cast<Dictionary<string, object>>()
            .SelectMany(d => d)
            .Where(p => p.Key == "fieldname1")
            .Select(p => p.Value).Cast<List<Dictionary<string,string>>>()
            .SelectMany(l => l)
            .SelectMany(d=> d)
            .Where(p => p.Key == "valueTitle")
            .Select(p => p.Value)
            .ToList();

这也有效，并且易于理解。