How to post JSON to a server using C

Question

Here s the code I m using      create a request HttpWebRequest request    HttpWebRequest  WebRequest Create url   request KeepAlive   false  request ProtocolVersion   HttpVersion Version10  request Method    POST        turn our request string into a byte stream byte   postBytes   Encoding UTF8 GetBytes json       this is important - make sure you specify type this way request ContentType    application json  charset UTF-8   request Accept    application json   request ContentLength   postBytes Length  request CookieContainer   Cookies  request UserAgent   currentUserAgent  Stream requestStream   request GetRequestStream        now send it requestStream Write postBytes  0  postBytes Length   requestStream Close        grab te response and print it out to the console along with the status code HttpWebResponse response    HttpWebResponse request GetResponse    string result  using  StreamReader rdr   new StreamReader response GetResponseStream           result   rdr ReadToEnd       return result    When I m running this  I m always getting 500 internal server error   What am I doing wrong

User · Answer

This option is not mentioned   using  var client   new HttpClient          client BaseAddress   new Uri  http   localhost 9000         client DefaultRequestHeaders Accept Add new MediaTypeWithQualityHeaderValue  application json          var foo   new User               user    Foo           password    Baz             await client PostAsJsonAsync  users add   foo

User · Answer

If you need to call is asynchronously then use  var request   HttpWebRequest Create  http   www maplegraphservices com tokkri webservices updateProfile php oldEmailID     App currentUser email  as HttpWebRequest              request Method    POST               request ContentType    text json               request BeginGetRequestStream new AsyncCallback GetRequestStreamCallback   request    private void GetRequestStreamCallback IAsyncResult asynchronousResult                HttpWebRequest request    HttpWebRequest asynchronousResult AsyncState             End the stream request operation          Stream postStream   request EndGetRequestStream asynchronousResult                Create the post data         string postData   JsonConvert SerializeObject edit  ToString             byte   byteArray   Encoding UTF8 GetBytes postData             postStream Write byteArray  0  byteArray Length           postStream Close               Start the web request         request BeginGetResponse new AsyncCallback GetResponceStreamCallback   request              void GetResponceStreamCallback IAsyncResult callbackResult                HttpWebRequest request    HttpWebRequest callbackResult AsyncState          HttpWebResponse response    HttpWebResponse request EndGetResponse callbackResult           using  StreamReader httpWebStreamReader   new StreamReader response GetResponseStream                           string result   httpWebStreamReader ReadToEnd                stat Text   result

User · Answer

Ademar s solution can be improved by leveraging JavaScriptSerializer s Serialize method to provide implicit conversion of the object to JSON   Additionally  it is possible to leverage the using statement s default functionality in order to omit explicitly calling Flush and Close   var httpWebRequest    HttpWebRequest WebRequest Create  http   url    httpWebRequest ContentType    application json   httpWebRequest Method    POST    using  var streamWriter   new StreamWriter httpWebRequest GetRequestStream           string json   new JavaScriptSerializer   Serialize new                                       user    Foo                       password    Baz                           streamWriter Write json      var httpResponse    HttpWebResponse httpWebRequest GetResponse    using  var streamReader   new StreamReader httpResponse GetResponseStream           var result   streamReader ReadToEnd

User · Answer

The HttpClient type is a newer implementation than the WebClient and HttpWebRequest  You can simply use the following lines  string myJson    quot   Username    myusername   Password   pass   quot   using  var client   new HttpClient          var response   await client PostAsync           quot http   yourUrl quot             new StringContent myJson  Encoding UTF8   quot application json quot        When you need your HttpClient more than once it s recommended to only create one instance and reuse it or use the new HttpClientFactory

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var data   Encoding ASCII GetBytes json    byte   postBytes   Encoding UTF8 GetBytes json    Use ASCII instead of UFT8

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WARNING  I have a very strong view on this subject    NET   s existing web clients are not developer friendly  WebRequest  amp  WebClient are prime examples of  how to frustrate a developer   They are verbose  amp  complicated to work with  when all you want to do is a simple Post request in C   HttpClient goes some way in addressing these issues  but it still falls short  On top of that Microsoft   s documentation is bad     really bad  unless you want to sift through pages and pages of technical blurb   Open-source to the rescue  There are three excellent open-source  free NuGet libraries as alternatives  Thank goodness  These are all well supported  documented and yes  easy - correction   super easy - to work with    ServiceStack Text - fast  light and resilient  RestSharp - simple REST and HTTP API Client Flurl- a fluent  portable  testable HTTP client library   There is not much between them  but I would give ServiceStack Text the slight edge       Github stars are roughly the same  Open Issues  amp  importantly how quickly any issues closed down  ServiceStack takes the award here for the fastest issue resolution  amp  no open issues  Documentation  All have great documentation  however  ServiceStack takes it to the next level  amp  is known for its    Golden standard    for documentation    Ok - so what does a Post Request in JSON look like within ServiceStack Text   var response    http   example org login       PostJsonToUrl new Login   Username  admin   Password  mypassword        That is one line of code  Concise  amp  easy  Compare the above to  NET   s Http libraries

User · Answer

Take care of the Content-Type you are using    application json   Sources    RFC4627  Other post

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Some different and clean way to achieve this is by using HttpClient like this   public async Task lt HttpResponseMessage gt  PostResult string url  ResultObject resultObject        using  var client   new HttpClient                  HttpResponseMessage response   new HttpResponseMessage            try                       response   await client PostAsJsonAsync url  resultObject                     catch  Exception ex                        throw ex                   return response

User · Answer

I find this to be the friendliest and most concise way to post an read JSON data  var url     quot http   www myapi com  quot   var request   new Request   Greeting    quot Hello world  quot     var json   JsonSerializer Serialize lt Request gt  request   using  WebClient client   new WebClient          var jsonResponse   client UploadString url  json       var response   JsonSerializer Deserialize lt Response gt  jsonResponse      I m using Microsoft s System Text Json for serializing and deserializing JSON  See NuGet

User · Answer

Further to Sean s post  it isn t necessary to nest the using statements  By using the StreamWriter it will be flushed and closed at the end of the block so no need to explicitly call the Flush   and Close   methods   var request    HttpWebRequest WebRequest Create  http   url    request ContentType    application json   request Method    POST    using  var streamWriter   new StreamWriter request GetRequestStream           string json   new JavaScriptSerializer   Serialize new                                       user    Foo                       password    Baz                           streamWriter Write json      var response    HttpWebResponse request GetResponse    using  var streamReader   new StreamReader response GetResponseStream               var result   streamReader ReadToEnd

User · Answer

I recently came up with a much simpler way to post a JSON  with the additional step of converting from a model in my app  Note that you have to make the model  JsonObject  for your controller to get the values and do the conversion     Request     var model   new MyModel       using  var client   new HttpClient            var uri   new Uri  XXXXXXXXX          var json   new JavaScriptSerializer   Serialize model        var stringContent   new StringContent json  Encoding UTF8   application json         var response   await Client PutAsync uri stringContent  Result                          Model     JsonObject   Serializable  public class MyModel       public Decimal Value   get  set        public string Project   get  set        public string FilePath   get  set        public string FileName   get  set        Server side    HttpPut       public async Task lt HttpResponseMessage gt  PutApi  FromBody MyModel model

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I finally invoked in sync mode by including the  Result  HttpResponseMessage response   null  try       using  var client   new HttpClient                 response   client PostAsync           http   localhost 8000                 new StringContent myJson Encoding UTF8  application json    Result      if  response IsSuccessStatusCode                        MessageBox Show  OK                                    else                       MessageBox Show  NOK                      catch  Exception ex        MessageBox Show  ERROR

User · Answer

The way I do it and is working is   var httpWebRequest    HttpWebRequest WebRequest Create  http   url    httpWebRequest ContentType    application json   httpWebRequest Method    POST    using  var streamWriter   new StreamWriter httpWebRequest GetRequestStream           string json       user     test                            password     bla           streamWriter Write json      var httpResponse    HttpWebResponse httpWebRequest GetResponse    using  var streamReader   new StreamReader httpResponse GetResponseStream           var result   streamReader ReadToEnd        I wrote a library to perform this task in a simpler way  it is here  https   github com ademargomes JsonRequest  Hope it helps

[c#] How to post JSON to a server using C#?

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