Serialize JSON String with customized format

Question

I have a Generic List object which hold below table as its own value.

CountryID | StateID | StateName
--------------------------------
    1     |  1      |  Alabama    
    1     |  2      |  California
    1     |  3      |  Florida
    1     |  4      |  Hawaii   
    2     |  5      |  London
    2     |  6      |  Oxford

I would like to create JSON string according to that List object. The JSON format which i would like to get is like below.

{           
    1: { '1': 'Alabama', '2': 'California', '3': 'Florida', '4': 'Hawaii' },
    2: { '5': 'London', '6': 'Oxford' }
};

I used below class to generate JSON object.

public static class JSONHelper
{
    public static string ToJSON(this object obj)
    {
        JavaScriptSerializer serializer = new JavaScriptSerializer();
        return serializer.Serialize(obj);
    }

    public static string ToJSON(this object obj, int recursionDepth)
    {
        JavaScriptSerializer serializer = new JavaScriptSerializer();
        serializer.RecursionLimit = recursionDepth;            
        return serializer.Serialize(obj);
    }
}

But , the actual output that I got when I finished calling ToJSON method is like below.

{
[

{"CountryID":1,"StateID":1,"StateName":"Alabama"},
{"CountryID":1,"StateID":2,"StateName":"California"},
{"CountryID":1,"StateID":3,"StateName":"Florida"},
{"CountryID":1,"StateID":4,"StateName":"Hawaii"},
{"CountryID":2,"StateID":5,"StateName":"London"},
{"CountryID":2,"StateID":6,"StateName":"Oxford"}

]
}

So , Could anyone please give me suggestion how could I make JSON string format as I want ?
Every suggestion will be appreciated.

Answer 1

You need to serialize a dictionary, not a list, to get that JSON. Given these type definitions:

public class Country
{
    public Country()
    {
        States = new List<State>();
    }
    public int         CountryID  { get; set; }
    public List<State> States     { get; set; }
}

public class State
{
    public int    StateID    { get; set; }
    public string StateName  { get; set; }
}

And this variable:

    var clist = new List<Country>();

I can serialize to the format you desire with this code:

    var d = clist.ToDictionary
        (k => k.CountryID.ToString(),
         e => e.States.ToDictionary(k2 => k2.StateID.ToString(),
                                    e2 => e2.StateName));

    Console.WriteLine("{0}",JSONHelper.ToJSON(d));

This uses the ToDictionary() extension method that is part of LINQ.

output:

{"1":{"1":"Lzwuoge","2":"0lzpas"},"2":{"1":"Mqn3ul5k","2":"Kefzu"}}

Answer 2

It seems like a simple way to do this would be to use LINQ to select into a dictionary, and then send the dictionary object to the JavascriptSerializer...

priveded we have:

var list = new[]
               {
                   new {CountryID = 1, StateID = 1, StateName = "Alabama"},
                   new {CountryID = 1, StateID = 2, StateName = "California"},
                   new {CountryID = 1, StateID = 3, StateName = "Florida"},
                   new {CountryID = 1, StateID = 4, StateName = "Hawaii"},
                   new {CountryID = 2, StateID = 5, StateName = "London"},
                   new {CountryID = 2, StateID = 6, StateName = "Oxford"}
               };

then we can call .ToDictionary recursively on it to get the following:

var d = list
    .GroupBy(x=>x.CountryID)
    .ToDictionary(g=> g.Key.ToString(), 
        g => g.ToDictionary(x => x.StateID.ToString(),x => x.StateName));

var serializer = new JavaScriptSerializer();
return serializer.Serialize(d);

which returns the JSON you requested

NOTE: you have to call the .ToString() on the dictionary Keys as the JavaScriptSerializer seems to fail on Dictionarys with keys that arent strings...

Answer 3

The simplest way to convert it to the format you specify is to convert your custom class to a nested dictionary:

Dictionary<Int32,Dictionary<String, String>>

and then serialize that output.

Dictionary<Int32,Dictionary<String, String>> countryDict= new Dictionary<Int32,Dictionary<String, String>>()
foreach(var item in myGenericList){
    Dictionary<Int32,Dictionary<String, String> stateDict = 
    countryDict[item.CountryID] ?? new Dictionary<Int32,Dictionary<String, String>>();
    stateDict.Add(item.StateID.ToString(),item.StateName) 
}