C#字典中的LINQ选择

Question

I have next dictionary in C#

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);

Is it possible to get all "valueTitle" with help of LINQ select?

UPDATE: Sorry, i should write it first - i need to get result from exitDictionary, not from subList

Answer 1

If you are searching by the fieldname1 value, try this:

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();

If you are looking by the type of the value in the subDictionary ( Dictionary<string, object> explicitly), you may do this:

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();

Both alternatives will return:

title1
title2
title3
title1
title2
title3

Answer 2

一种方法是首先使用SelectMany将列表展平：

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

Answer 3

这将返回与您的键valueTitle匹配的所有值

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();

This also works, and easy to understand.