MVC How to Return a String as JSON

Question

In an effort to make a progress reporting process a little more reliable and decouple it from the request response  I am performing the processing in a Windows Service and persisting the intended response to a file   When the client starts polling for updates  the intention is that the controller returns the contents of the file  whatever they are  as a JSON string   The contents of the file are pre-serialized to JSON   This is to ensure that there is nothing standing in the way of the response   No processing needs to happen  short of reading the file contents into a string and returning it  to get the response   I initially though this would be fairly simple  but it is not turning out to be the case   Currently my controller method looks thusly   Controller  Updated   HttpPost  public JsonResult UpdateBatchSearchMembers         string path   Properties Settings Default ResponsePath      string returntext      if   System IO File Exists path           returntext   Properties Settings Default EmptyBatchSearchUpdate      else         returntext   System IO File ReadAllText path        return this Json returntext       And Fiddler is returning this as the raw response  HTTP 1 1 200 OK Server  ASP NET Development Server 10 0 0 0 Date  Mon  19 Mar 2012 20 30 05 GMT X-AspNet-Version  4 0 30319 X-AspNetMvc-Version  3 0 Cache-Control  private Content-Type  application json  charset utf-8 Content-Length  81 Connection  Close      StopPolling   false   BatchSearchProgressReports        MemberStatuses          AJAX  Updated  The following will likely be changed later  but for now this was working when I was generating the response class and returning it as JSON like a normal person   this CheckForUpdate   function      var parent   this   if  this BatchSearchId    null  amp  amp  WorkflowState SelectedSearchList              showAjaxLoader   false      if  progressPending    true            progressPending   true            ajax               url  WorkflowState UpdateBatchLink     SearchListID     WorkflowState SelectedSearchList              type   POST               contentType   application json  charset utf-8               cache  false              success  function  data                    for  var i   0  i  lt  data MemberStatuses length  i                          var response   data MemberStatuses i                       parent UpdateCellStatus response                                     if  data StopPolling   true                        parent StopPullingForUpdates                                      showAjaxLoader   true                                    progressPending   false

User · Answer

You just need to return standard ContentResult and set ContentType to "application/json". You can create custom ActionResult for it:

public class JsonStringResult : ContentResult
{
    public JsonStringResult(string json)
    {
        Content = json;
        ContentType = "application/json";
    }
}

And then return it's instance:

[HttpPost]
public JsonResult UpdateBatchSearchMembers()
{
    string returntext;
    if (!System.IO.File.Exists(path))
        returntext = Properties.Settings.Default.EmptyBatchSearchUpdate;
    else
        returntext = Properties.Settings.Default.ResponsePath;

    return new JsonStringResult(returntext);
}

User · Answer

Yeah that s it without no further issues  to avoid raw string json this is it       public ActionResult GetJson                 var json   System IO File ReadAllText              Server MapPath     App Data content json              return new ContentResult                       Content   json              ContentType    application json               ContentEncoding   Encoding UTF8                     NOTE  please note that method return type of JsonResult is not working for me  since JsonResult and ContentResult both inherit ActionResult but there is no relationship between them

User · Answer

Use the following code in your controller   return Json new   success   string    JsonRequestBehavior AllowGet     and in JavaScript   success  function  data        var response   data success

User · Answer

All answers here provide good and working code  But someone would be dissatisfied that they all use ContentType as return type and not JsonResult    Unfortunately JsonResult is using JavaScriptSerializer without option to disable it  The best way to get around this is to inherit JsonResult   I copied most of the code from original JsonResult and created JsonStringResult class that returns passed string as application json  Code for this class is below  public class JsonStringResult   JsonResult               public JsonStringResult string data                        JsonRequestBehavior   JsonRequestBehavior DenyGet              Data   data                     public override void ExecuteResult ControllerContext context                        if  context    null                                throw new ArgumentNullException  context                              if  JsonRequestBehavior    JsonRequestBehavior DenyGet  amp  amp                  String Equals context HttpContext Request HttpMethod   GET   StringComparison OrdinalIgnoreCase                                 throw new InvalidOperationException  Get request is not allowed                                HttpResponseBase response   context HttpContext Response               if   String IsNullOrEmpty ContentType                                 response ContentType   ContentType                            else                               response ContentType    application json                             if  ContentEncoding    null                                response ContentEncoding   ContentEncoding                            if  Data    null                                response Write Data                                   Example usage   var json   JsonConvert SerializeObject data   return new JsonStringResult json

User · Answer

The issue  I believe  is that the Json action result is intended to take an object  your model  and create an HTTP response with content as the JSON-formatted data from your model object   What you are passing to the controller s Json method  though  is a JSON-formatted string object  so it is  serializing  the string object to JSON  which is why the content of the HTTP response is surrounded by double-quotes  I m assuming that is the problem    I think you can look into using the Content action result as an alternative to the Json action result  since you essentially already have the raw content for the HTTP response available   return this Content returntext   application json       not sure off-hand if you should also specify  charset utf-8  here       or if that is done automatically   Another alternative would be to deserialize the JSON result from the service into an object and then pass that object to the controller s Json method  but the disadvantage there is that you would be de-serializing and then re-serializing the data  which may be unnecessary for your purposes

[asp.net-mvc] MVC: How to Return a String as JSON

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