How do I convert a dictionary to a JSON String in C

Question

I want to convert my Dictionary lt int List lt int gt  gt  to JSON string  Does anyone know how to achieve this in C

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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 lt int List lt int gt  gt  MyObj   new Dictionary lt int List lt int gt  gt        Populate it here     string myJsonString    new JavaScriptSerializer    Serialize MyObj

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You can use System Web Script Serialization JavaScriptSerializer   Dictionary lt string  object gt  dictss   new Dictionary lt string  object gt          User    Mr Joshua         Pass    4324        string jsonString    new JavaScriptSerializer    Serialize  object dictss

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Simple One-Line Answer   using System Web Script Serialization    This code will convert any Dictionary lt Key Value gt  to Dictionary lt string string gt  and then serialize it as a JSON string   var json   new JavaScriptSerializer   Serialize yourDictionary ToDictionary item   gt  item Key ToString    item   gt  item Value ToString        It is worthwhile to note that something like Dictionary lt int  MyClass gt  can also be serialized in this way while preserving the complex type object     Explanation  breakdown   var yourDictionary   new Dictionary lt Key Value gt       This is just to represent your current Dictionary    You can replace the variable yourDictionary with your actual variable   var convertedDictionary   yourDictionary ToDictionary item   gt  item Key ToString    item   gt  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

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using System  using System Collections Generic  using System Linq  using System Text  using System Runtime Serialization Json  using System IO   namespace ConsoleApplication1       class Program               static void Main string   args                        Dictionary lt int  List lt int gt  gt  foo   new Dictionary lt int  List lt int gt  gt                  foo Add 1  new List lt int gt   new int     1  2  3  4                  foo Add 2  new List lt int gt  new int     2  3  4  1                  foo Add 3  new List lt int gt  new int     3  4  1  2                  foo Add 4  new List lt int gt  new int     4  1  2  3                   DataContractJsonSerializer serializer   new DataContractJsonSerializer typeof Dictionary lt int  List lt int gt  gt                  using  MemoryStream ms   new MemoryStream                                  serializer WriteObject ms  foo                   Console WriteLine Encoding Default GetString ms ToArray                                        This will write to the console       Key   1   Value    1 2 3 4      Key   2   Value    2 3 4 1      Key   3   Value    3 4 1 2      Key   4   Value    4 1 2 3

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Here s how to do it using only standard  Net libraries from Microsoft      using System IO  using System Runtime Serialization Json   private static string DataToJson lt T gt  T data        MemoryStream stream   new MemoryStream         DataContractJsonSerializer serialiser   new DataContractJsonSerializer          data GetType            new DataContractJsonSerializerSettings                         UseSimpleDictionaryFormat   true                  serialiser WriteObject stream  data        return Encoding UTF8 GetString stream ToArray

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This answer mentions Json NET but stops short of telling you how you can use Json NET to serialize a dictionary   return JsonConvert SerializeObject  myDictionary      As opposed to JavaScriptSerializer  myDictionary does not have to be a dictionary of type  lt string  string gt  for JsonConvert to work

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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 lt int  List lt int gt  gt  as you have specified  you can use Linq   string MyDictionaryToJson Dictionary lt int  List lt int gt  gt  dict        var entries   dict Select d   gt          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

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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 lt string  List lt string gt  gt  myDict  string outputfilename                DataContractJsonSerializer js   new DataContractJsonSerializer typeof Dictionary lt string  List lt string gt  gt             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   gt    abc   def   ghi   StringKeyofDictionary2   gt    String01   String02   String03   String04   Stringkey3   gt    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

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This is Similar to what Meritt has posted earlier  just posting the complete code      string sJSON      Dictionary lt string  string gt  aa1   new Dictionary lt string  string gt         aa1 Add  one    1    aa1 Add  two    2    aa1 Add  three    3        Console Write  JSON form of Person object           sJSON   WriteFromObject aa1       Console WriteLine sJSON        Dictionary lt string  string gt  aaret   new Dictionary lt string  string gt         aaret   ReadToObject lt Dictionary lt string  string gt  gt  sJSON        public static string WriteFromObject object obj                            byte   json                Create a stream to serialize the object to            using  MemoryStream ms   new MemoryStream                                             Serializer the object to the stream                DataContractJsonSerializer ser   new DataContractJsonSerializer obj GetType                 ser WriteObject ms  obj               json   ms ToArray                ms Close                      return Encoding UTF8 GetString json  0  json Length                  Deserialize a JSON stream to object        public static T ReadToObject lt T gt  string json  where T   class  new                 T deserializedObject   new T            using  MemoryStream ms   new MemoryStream Encoding UTF8 GetBytes json                           DataContractJsonSerializer ser   new DataContractJsonSerializer deserializedObject GetType                 deserializedObject   ser ReadObject ms  as T              ms Close                      return deserializedObject

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If your context allows it  technical constraints  etc    use the JsonConvert SerializeObject method from Newtonsoft Json   it will make your life easier   Dictionary lt string  string gt  localizedWelcomeLabels   new Dictionary lt string  string gt     localizedWelcomeLabels Add  en    Welcome    localizedWelcomeLabels Add  fr    Bienvenue    localizedWelcomeLabels Add  de    Willkommen    Console WriteLine JsonConvert SerializeObject localizedWelcomeLabels        Outputs     en   Welcome   fr   Bienvenue   de   Willkommen

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Json NET probably serializes C  dictionaries adequately now  but when the OP originally posted this question  many MVC developers may have been using the JavaScriptSerializer class because that was the default option out of the box   If you re working on a legacy project  MVC 1 or MVC 2   and you can t use Json NET  I recommend that you use a List lt KeyValuePair lt K V gt  gt  instead of a Dictionary lt K V gt  gt   The legacy JavaScriptSerializer class will serialize this type just fine  but it will have problems with a dictionary   Documentation  Serializing Collections with Json NET

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Just for reference  among all the older solutions  UWP has its own built-in JSON library  Windows Data Json  JsonObject is a map that you can use directly to store your data  var options   new JsonObject    options  quot foo quot     JsonValue CreateStringValue  quot bar quot    string json   options ToString

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In Asp net Core use   using Newtonsoft Json  var obj   new   MyValue   1    var json   JsonConvert SerializeObject obj   var obj2   JsonConvert DeserializeObject json

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You could use JavaScriptSerializer

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