How do I convert a dictionary to a JSON String in

Question

I want to convert my Dictionary<int,List<int>> to JSON string. Does anyone know how to achieve this in C#?

Answer 1

Simple One-Line Answer

(using System.Web.Script.Serialization )

This code will convert any Dictionary<Key,Value> to Dictionary<string,string> and then serialize it as a JSON string:

var json = new JavaScriptSerializer().Serialize(yourDictionary.ToDictionary(item => item.Key.ToString(), item => item.Value.ToString()));

It is worthwhile to note that something like Dictionary<int, MyClass> can also be serialized in this way while preserving the complex type/object.

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Explanation (breakdown)

var yourDictionary = new Dictionary<Key,Value>(); //This is just to represent your current Dictionary.

You can replace the variable yourDictionary with your actual variable.

var convertedDictionary = yourDictionary.ToDictionary(item => item.Key.ToString(), item => item.Value.ToString()); //This converts your dictionary to have the Key and Value of type string.

We do this, because both the Key and Value has to be of type string, as a requirement for serialization of a Dictionary.

var json = new JavaScriptSerializer().Serialize(convertedDictionary); //You can then serialize the Dictionary, as both the Key and Value is of type string, which is required for serialization.

Answer 2

In Asp.net Core use:

using Newtonsoft.Json

var obj = new { MyValue = 1 };
var json = JsonConvert.SerializeObject(obj);
var obj2 = JsonConvert.DeserializeObject(json);

Answer 3

You can use System.Web.Script.Serialization.JavaScriptSerializer:

Dictionary<string, object> dictss = new Dictionary<string, object>(){
   {"User", "Mr.Joshua"},
   {"Pass", "4324"},
};

string jsonString = (new JavaScriptSerializer()).Serialize((object)dictss);

Answer 4

Serializing data structures containing only numeric or boolean values is fairly straightforward. If you don't have much to serialize, you can write a method for your specific type.

For a Dictionary<int, List<int>> as you have specified, you can use Linq:

string MyDictionaryToJson(Dictionary<int, List<int>> dict)
{
    var entries = dict.Select(d =>
        string.Format("\"{0}\": [{1}]", d.Key, string.Join(",", d.Value)));
    return "{" + string.Join(",", entries) + "}";
}

But, if you are serializing several different classes, or more complex data structures, or especially if your data contains string values, you would be better off using a reputable JSON library that already knows how to handle things like escape characters and line breaks. Json.NET is a popular option.

Answer 5

It seems a lot of different libraries and what not have seem to come and go over the previous years. However as of April 2016, this solution worked well for me. Strings easily replaced by ints.

TL/DR; Copy this if that's what you came here for:

    //outputfilename will be something like: "C:/MyFolder/MyFile.txt"
    void WriteDictionaryAsJson(Dictionary<string, List<string>> myDict, string outputfilename)
    {
        DataContractJsonSerializer js = new DataContractJsonSerializer(typeof(Dictionary<string, List<string>>));
        MemoryStream ms = new MemoryStream();
        js.WriteObject(ms, myDict); //Does the serialization.

        StreamWriter streamwriter = new StreamWriter(outputfilename);
        streamwriter.AutoFlush = true; // Without this, I've run into issues with the stream being "full"...this solves that problem.

        ms.Position = 0; //ms contains our data in json format, so let's start from the beginning
        StreamReader sr = new StreamReader(ms); //Read all of our memory
        streamwriter.WriteLine(sr.ReadToEnd()); // and write it out.

        ms.Close(); //Shutdown everything since we're done.
        streamwriter.Close();
        sr.Close();
    }

Two import points. First, be sure to add System.Runtime.Serliazation as a reference in your project inside Visual Studio's Solution Explorer. Second, add this line,

using System.Runtime.Serialization.Json;

at the top of the file with the rest of your usings, so the DataContractJsonSerializer class can be found. This blog post has more information on this method of serialization.

Data Format (Input / Output)

My data is a dictionary with 3 strings, each pointing to a list of strings. The lists of strings have lengths 3, 4, and 1. The data looks like this:

StringKeyofDictionary1 => ["abc","def","ghi"]
StringKeyofDictionary2 => ["String01","String02","String03","String04"]
Stringkey3 => ["someString"]

The output written to file will be on one line, here is the formatted output:

 [{
     "Key": "StringKeyofDictionary1",
     "Value": ["abc",
     "def",
     "ghi"]
 },
 {
     "Key": "StringKeyofDictionary2",
     "Value": ["String01",
     "String02",
     "String03",
     "String04",
 ]
 },
 {
     "Key": "Stringkey3",
     "Value": ["SomeString"]
 }]

Answer 6

Sorry if the syntax is the tiniest bit off, but the code I'm getting this from was originally in VB :)

using System.Web.Script.Serialization;

...

Dictionary<int,List<int>> MyObj = new Dictionary<int,List<int>>();

//Populate it here...

string myJsonString = (new JavaScriptSerializer()).Serialize(MyObj);