How to write a JSON file in C

Question

I need to write the following data into a text file using JSON format in C   The brackets are important for it to be valid JSON format              Id   1       SSN   123       Message    whatever                Id   2       SSN   125       Message    whatever          Here is my model class   public class data       public int Id   get  set        public int SSN   get  set        public string Message   get  set

User · Answer

var responseData     Fetch Data string jsonData   JsonConvert SerializeObject responseData  Formatting None   System IO File WriteAllText Server MapPath    JsonData jsondata txt    jsonData

User · Answer

Update 2020  It s been 7 years since I wrote this answer  It still seems to be getting a lot of attention  In 2013 Newtonsoft Json Net was THE answer to this problem  Now it s still a good answer to this problem but it s no longer the the only viable option  To add some up-to-date caveats to this answer    Net Core now has the spookily similar System Text Json serialiser  see below  The days of the JavaScriptSerializer have thankfully passed and this class isn t even in  Net Core  This invalidates a lot of the comparisons ran by Newtonsoft  It s also recently come to my attention  via some vulnerability scanning software we use in work that Json Net hasn t had an update in some time  Updates in 2020 have dried up and the latest version  12 0 3  is over a year old  The speed tests quoted below are comparing an older version of Json Nt  version 6 0 and like I said the latest is 12 0 3  with an outdated  Net Framework serialiser   Are Json Net s days numbered  It s still used a LOT and it s still used by MS librarties  So probably not  But this does feel like the beginning of the end for this library that may well of just run it s course   Update since  Net Core 3 0 A new kid on the block since writing this is System Text Json which has been added to  Net Core 3 0  Microsoft makes several claims to how this is  now  better than Newtonsoft  Including that it is faster than Newtonsoft  as below  I d advise you to test this yourself    I would recommend Json Net  see example below  List lt data gt   data   new List lt data gt      data Add new data         Id   1      SSN   2      Message    quot A Message quot       string json   JsonConvert SerializeObject  data ToArray        write string to file System IO File WriteAllText   quot D  path txt quot   json    Or the slightly more efficient version of the above code  doesn t use a string as a buffer     open file stream using  StreamWriter file   File CreateText   quot D  path txt quot           JsonSerializer serializer   new JsonSerializer           serialize object directly into file stream      serializer Serialize file   data      Documentation  Serialize JSON to a file  Why  Here s a feature comparison between common serialisers as well as benchmark tests    Below is a graph of performance taken from the linked article   This separate post  states that   Json NET has always been memory efficient  streaming the reading and writing large documents rather than loading them entirely into memory  but I was able to find a couple of key places where object allocations could be reduced        now  Json Net  6 0  allocates 8 times less memory than JavaScriptSerializer     Benchmarks appear to be Json Net 5  the current version  on writing  is 10  What version of standard  Net serialisers used is not mentioned  These tests are obviously from the developers who maintain the library  I have not verified their claims  If in doubt test them yourself

User · Answer

The example in Liam s answer saves the file as string in a single line  I prefer to add formatting  Someone in the future may want to change some value manually in the file  If you add formatting it s easier to do so   The following adds basic JSON indentation    string json   JsonConvert SerializeObject  data ToArray    Formatting Indented

User · Answer

There is built in functionality for this using the JavaScriptSerializer Class   var json   JavaScriptSerializer Serialize data

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