C# How to sort nested dictionary by value

Question

Okay, what I am trying to accomplish here is I have a dictionary with data that looks like this:

Unsorted:

US ( total population: 9 )
-New York - 4
-Miami - 5
Spain ( total population: 4 )
-Madrid - 3
-Barcelona - 1
France ( total population: 7 )
-Paris - 7

I need to sort the dictionaries by Country with largest population and then every city by largest population so it looks something like this:

Sorted:

US ( total population: 9 )
-Miami - 5
-New York - 4
France ( total population: 7 )
-Paris - 7
Spain ( total population: 4 )
-Madrid - 3
-Barcelona - 1

I have:

var worldPopulation = new Dictionary<string, Dictionary<string, long>>();

I already sorted the countries using this line of code:

worldPopulation = worldPopulation.OrderByDescending(x => x.Value.Values.Sum()).ToDictionary(x => x.Key, x => x.Value);

But I am struggling to find a solution for sorting the nested dictionary with the countries.

I am trying to do this with a single linq statement, but if its not possible a foreach solution would also be appreciated. Thanks!

EDIT:

@J_L's solution was exactly what I was looking for:

 worldPopulation = worldPopulation.OrderByDescending(x => x.Value.Values.Sum()).ToDictionary(x => x.Key, x => x.Value.OrderByDescending(y => y.Value).ToDictionary(y => y.Key, y => y.Value));

@Lucifer's solution also made it work:

var worldPopulationSorted = new Dictionary<string, Dictionary<string, long>>();

worldPopulation.OrderByDescending(dic => dic.Value.Values.Sum()).ToList().ForEach(x => worldPopulationSorted.Add(x.Key, x.Value.OrderByDescending(y => y.Value).ToDictionary(y => y.Key, y => y.Value)));

I understand that some of you are telling me to use a different approach, so will try using lists as some of you suggested. I also learned some new things, so thanks to everyone for the help.

items order in dictionary has no meaning. Access is done by key. If you want it sorted maybe consider a different data structure. For instance instead of calling `.ToDictionary` store it in a list of tuple or so. Also have a look at [How do you sort a dictionary by value?](https://stackoverflow.com/q/289/6400526) — Gilad Green, Jun 13 '18 at 12:23
your using the wrong collection dictionaries have not order you want a SortedList — MikeT, Jun 13 '18 at 12:31

Lucifer · Answer 1 · 2018-06-13T13:35:43.307

0

Here is a working example of what you need :-

var worldPopulationSorted = new Dictionary<string, Dictionary<string, long>>();

worldPopulation.OrderByDescending(dic => dic.Value.Values.Sum()).ToList().ForEach(x => worldPopulationSorted.Add(x.Key, x.Value.OrderByDescending(y => y.Value).ToDictionary(y => y.Key, y => y.Value)));

Example which I used:-

var worldPopulation = new Dictionary<string, Dictionary<string, long>>();

Dictionary<string, long> sample = new Dictionary<string, long>();
sample.Add("1", 5);
sample.Add("2", 6);
sample.Add("3", 7);

worldPopulation.Add("first", sample);

sample = new Dictionary<string,long>();
sample.Add("3", 9);
sample.Add("2", 9);
sample.Add("1", 9);

worldPopulation.Add("second", sample);

var worldPopulationSorted = new Dictionary<string, Dictionary<string, long>>();

worldPopulation.OrderByDescending(dic => dic.Value.Values.Sum()).ToList().ForEach(x => worldPopulationSorted.Add(x.Key, x.Value.OrderByDescending(y => y.Value).ToDictionary(y => y.Key, y => y.Value)));

output:-

second
   3 - 9
   2 - 9
   1 - 9
first
   3 - 7
   2 - 6
   1 - 5

FootNote:- you really need to change the structure of your data cause if the data is in large amount then it will be really difficult to handle

edited Jun 13 '18 at 13:35

answered Jun 13 '18 at 12:54

Lucifer

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This works, because the existing `Dictionary` returns entries in the same order you added them (unless you remove entries). Note this is an implementation detail only - Microsoft doesn't guarantee that behaviour going forward. As such, this is not recommended. – mjwills Jun 13 '18 at 13:39
But I don't understand the reason of down-vote this answer solves Op's req. – Lucifer Jun 13 '18 at 13:41
1

Code has contracts and implementations. The contract says 'this is what I promise - rely on this'. The implementation says 'this is how I work **right now**'. You are relying on the **implementation** when you should be relying on the contract. The docs clearly state (https://msdn.microsoft.com/en-us/library/xfhwa508(v=vs.110).aspx#Anchor_7) - `For purposes of enumeration, each item in the dictionary is treated as a KeyValuePair structure representing a value and its key. The order in which the items are returned is undefined.`. The order is undefined - you can't rely on it. – mjwills Jun 13 '18 at 13:45
@mjwills Now I understood what are you trying to convey, the Op here is using a Dictionary but as suggested by you guys he should be using a `SortedListt` to achieve whatever he is trying to achieve.I will edit the answer with a sorted List/dictionary solution – Lucifer Jun 13 '18 at 13:49
I am not convinced a `SortedList` will work either, but give it a try. – mjwills Jun 13 '18 at 13:50
@mjwills Considering the structure of the OP it is difficult to do so, you suggest what should I do delete the answer or let OP decide ? – Lucifer Jun 13 '18 at 14:02

score 0 · Accepted Answer · answered Jun 13 '18 at 13:11

I think this is what you are looking for:

var worldPopulation = new Dictionary<string, Dictionary<string, long>>()
{
    {"US", new Dictionary<string, long>()
    {
        { "New York", 4 },
        { "Miami", 5 }
    }},
    {"Spain", new Dictionary<string, long>()
    {
        { "Madrid", 3 },
        { "Barcelona", 1 },
    }},
    {"France", new Dictionary<string, long>()
    {
        { "Paris", 7 },
    }},
};


worldPopulation = worldPopulation.OrderByDescending(x => x.Value.Values.Sum()).
    ToDictionary(x => x.Key, 
    x => x.Value.OrderByDescending(y => y.Value).ToDictionary(y => y.Key, y => y.Value));

foreach (var country in worldPopulation)
{
    Console.WriteLine(country.Key);
    foreach (var city in country.Value)
        Console.WriteLine("   " + city.Key + " - " + city.Value);
}

Output:

US Miami - 5 New York - 4 France Paris - 7 Spain Madrid - 3 Barcelona - 1

C# How to sort nested dictionary by value

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