MVC: How to Return a String as JSON
asp.net MvcJsonasp.net Mvc Problem Overview
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 && 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 < data.MemberStatuses.length; i++) {
var response = data.MemberStatuses[i];
parent.UpdateCellStatus(response);
}
if (data.StopPolling = true) {
parent.StopPullingForUpdates();
}
showAjaxLoader = true;
}
});
progressPending = false;
}
}
asp.net Mvc Solutions
Solution 1 - asp.net Mvc
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.
Solution 2 - asp.net Mvc
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);
}
Solution 3 - asp.net Mvc
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.
Solution 4 - asp.net Mvc
Use the following code in your controller:
return Json(new { success = string }, JsonRequestBehavior.AllowGet);
and in JavaScript:
success: function (data) {
var response = data.success;
....
}
Solution 5 - asp.net Mvc
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 &&
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);