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String does not act as valid json object when returned from Controller

I'm trying to read a string from a json response however I get an error:
SyntaxError: Unexpected token c in JSON at position
I have a controller which returns a guid as a string from the DB
[HttpPost("TransactionOrderId/{id}")]
public async Task<string> TransactionOrderId(int id)
{
return await this._service.GetTransactionOrderId(id);
}
In my Angular 2 application I'm subscribing to my provider which has trouble parsing my response from my server.
this.meetingsProvider.getTransactionOrderId(this.meetingId).subscribe((transactionId: string) => {
this.transactionOrderId = transactionId;
});
And My Provider code looks like so:
getTransactionOrderId(meetingId: number): Observable<string> {
const headers = new Headers();
headers.append('Content-Type', 'application/json');
return this.http.post(`${this.apiUrl}/${this.route}/transactionOrderId/${meetingId}`, null, {
headers: headers
}).map(res => <string>res.json());
}
My Server Responds with the proper transaction order id the response looks like so:
status: 200
statusText: "OK"
type: 2
url: "http://localhost/api/meetings/transactionOrderId/4"
_body: "0c290d50-8d72-4128-87dd-eca8b58db3fe"
I have other api calls using the same code that return bool which return fine, but when I try to return string I get a parsing error why?

That's not a valid JSON object, that's why you get that error. A JSON object starts with { and ends with }.
If you want to be able to JSON-deserialize that, use:
public async Task<JsonResult> TransactionOrderId(int id)
{
return Json(await this._service.GetTransactionOrderId(id));
}
Note that if you return anything that is not a string, ASP.NET Core should JSON-serialize it (that's the default serializer anyway).

Invaild Json Result through Web Api in angular js

I have build a http post web api in asp which return the following string in Json
RootObject rootObject = new RootObject()
{
status = "User Registered"
};
msg = JsonConvert.SerializeObject(rootObject);
Below is my angular js controller in which I am consuming that web api
.controller('signupCtrl', function($scope,$http,$ionicPopup,$state,$ionicHistory) {
$scope.signup=function(data){
var link = 'http://xxxxxxxxxxxxxxxxxxxxxx/api/Home/RegisterUser';
//using http post
//passing values to parameter
$http.post(link, {RegisterName : data.name, RegisterUserName : data.username, RegisterPassword : data.password , RegisterEmail: data.mail , RegisterMobile : data.mobile})
.then(function (res){ //if a response is recieved from the server.
$scope.response = res; //contains Register Result
console.log($scope.response);
});
}
})
With the above code I am getting following result in google chrome console
I am try to get that status only to match it value but I am unable to do so.
The doubt I am having is that json format

console.log(JSON.stringify($scope.response)) will do what you need.
If you're wanting those particular value, you can just access those and pass them to log.
console.log($scope.response.data['status']);

you get the json as :
$scope.response = res.data;
might be you require JSON.parse(res.data) or $.parseJSON(res.data) for getting json object

Failed to serialize the response body after upgrading from ODATA v3 to v4

I have a Web API server where I use ODATA (and EF 6) to return a list of Items (consumed by a WinForms client that uses a DevExpress ODataInstantFeedbackSource bound to their GridControl).
Here is the Web API controller method that returns the list of Items:
public IHttpActionResult GetItems(ODataQueryOptions<Item> queryOptions)
{
var customerNumber = Request.Headers.GetValues("CustomerNumber").FirstOrDefault();
try
{
queryOptions.Validate(_validationSettings);
var query = queryOptions.ApplyTo(Context.Items) as IQueryable<Item>;
var items = query.AsEnumerable().Select(i => new Item()
{
ItemNumber = i.ItemNumber,
ItemDescription = i.ItemDescription,
<snip>
RebateAmount = RebateUtil.CalculateInstantRebates(i.ItemNo, customerNumber),
}).AsQueryable();
return Ok(items);
}
catch (ODataException ex)
{
return BadRequest(ex.Message);
}
}
Before I upgraded to ODATA v3, the above was working perfectly; after upgrading, I now get:
The ObjectContent1 type failed to serialize the response body for
content type "text/plain; charset=utf-8", The value of type
"System.Linq.EnumerableQuery1[[AcmeService.Model.Item,
AcmeService.Model, Version=1.0.0.0, Culture=neutral,
PublicKeyToken=null]]" could not be converted to a raw string.
I see the above message in the HTTP response body (Status 500). The request URL is: http://acme.us/odata/Items/$count
Note that if I make the GetItems controller simply do a "return Ok(Context.Items)", it works fine (no error, but I need to be able to set the RebateAmount value before returning the data).
What am I doing wrong?

I had the same error message in an another context (without devexpress), but maybe this could help you.
I solved it by replacing this namespace :
using System.Web.Http.OData;
by :
using System.Web.OData;

Content Negotiation in ASP.NET Web API

I'm migrating a web service to ASP.NET Web Api 2, and hitting trouble at almost the first hurdle.
I want to do this:
public class SomeController : ApiController
{
[Route("some\url")]
public object Get()
{
return { Message = "Hello" };
}
}
And be able to ask the service for either "application/json" or "application/xml" (or indeed any other potential format, such as Message Pack), and get a serialized response. But it seems it only works for JSON.
I've read this and seen the documentation which states clearly that the framework cannot handle serialization of anonymous types into XML (seriously) and that the solution is to not use XML (seriously).
When I attempt to call this and request XML as response type, I get
The 'ObjectContent`1' type failed to serialize the response body for content type 'application/xml; charset=utf-8'.
I'm not removing support for clients wanting to ask for XML - but I genuinely can't find a work around for this - what can I do?
Edit
I've added these:
System.Web.Http.GlobalConfiguration.Configuration.Formatters.XmlFormatter.SupportedMediaTypes.Clear();
config.Formatters.Insert(0, new System.Net.Http.Formatting.JsonMediaTypeFormatter());
config.Formatters.Insert(0, new System.Net.Http.Formatting.XmlMediaTypeFormatter());
as per Dalorzo's answer, but it made no difference.
For clarification, the service works absolutely fine when I call it using an accept header of application/json, but bombs when I call it with an accept header of application/xml.

You have 3 options:
Create a class with a proper name and return the object instead of an anonymous type.
Or if you want to return the anonymous instance, you should remove XML formatter, because anonymous types are not supported by XML Formatter
Create your own formatter inheriting from MediaTypeFormatter or BufferedMediaTypeFormatter

You can do it by following code :
public HttpResponseMessage GetTestData()
{
var testdata = (from u in context.TestRepository.Get().ToList()
select
new Message
{
msgText = u.msgText
});
return ActionContext.Request.CreateResponse(HttpStatusCode.OK, testdata);
}

// This Code Is Used To Change Contents In Api
public HttpResponseMessage GetAllcarDetails( string formate)
{
CarModel ST = new CarModel();
CarModel ST1 = new CarModel();
List<CarModel> li = new List<CarModel>();
ST.CarName = "Maruti Waganor";
ST.CarPrice = 400000;
ST.CarModeles = "VXI";
ST.CarColor = "Brown";
ST1.CarName = "Maruti Swift";
ST1.CarPrice = 500000;
ST1.CarModeles = "VXI";
ST1.CarColor = "RED";
li.Add(ST);
li.Add(ST1);
// return li;
this.Request.Headers.Accept.Add(
new MediaTypeWithQualityHeaderValue("application/xml"));
//For Json Use "application/json"
IContentNegotiator negotiator =
this.Configuration.Services.GetContentNegotiator();
ContentNegotiationResult result = negotiator.Negotiate(
typeof(List<CarModel>), this.Request, this.Configuration.Formatters);
if (result == null) {
var response = new HttpResponseMessage(HttpStatusCode.NotAcceptable);
throw new HttpResponseException(response);
}
return new HttpResponseMessage() {
Content = new ObjectContent<List<CarModel>>(
li, // What we are serializing
result.Formatter, // The media formatter
result.MediaType.MediaType // The MIME type
)
};
}

Please browse your API route on Chrome. Chrome, by default shows output in XML format. If that doesn't happen, it means that your service is preventing XML format using media formatting.
And in that case, you should search your WebApiConfig. If nothing is present there, add this file to your project
using System.Net.Http.Formatting;
using System.Collections.Generic;
using System.Net.Http;
using System;
using System.Linq;
using System.Net.Http.Headers;
namespace ExampleApp.Infrastructure
{
public class CustomNegotiator : DefaultContentNegotiator
{
public override ContentNegotiationResult Negotiate(Type type, HttpRequestMessage request, IEnumerable<MediaTypeFormatter> formatters)
{
if(request.Headers.UserAgent.Where(x=>x.Product!=null&& x.Product.Name.ToLower().Equals("chrome")).Count() > 0)
{
return new ContentNegotiationResult(new JsonMediaTypeFormatter(), new MediaTypeHeaderValue("application/xml"));
}
else
{
return base.Negotiate(type, request, formatters);
}
}
}
}
and, in WebApiConfig.cs, add:
config.Services.Replace(typeof(IContentNegotiator), new CustomNegotiator());

Android -- How to access data in an ASP.NET database via app?

I have a Windows web server already set up with a website (unlimited application pools) and I want to be able to access a database on that server via the Android app I'm developing. How can I do this? Can someone point me to a tutorial or give code example of how this cross-platform (Android/Java to ASP.NET/C#) communication can be done?
(I'm trying to create a leader board or global scoreboard for my Android game on my server.)
Thanks.

Your app should expose a webservice.
There is no native support for .net soap based webservices. But you can use the ksoap android port:
http://code.google.com/p/ksoap2-android/
which allows an android app to consume a .net asmx webservice.
However the deserialisation of complex on the client side involves lot of code writing for every object you want so pass to the client.
I tried it for a project and there were some problems I ran into (either I could get result back to the client but the parameters i passed where always null or the other way - I could pass arguments but the result was null).
Here is an example I posted for getting an int: How to call a .NET Webservice from Android using KSOAP2?
However, from my current knowlege I would suggest using a .asmx webservice that returns a json string and use a java json serialiser to parse the output. The advantages:
Write less code
Faster, since mobile devices don't always have good internet connections and the xml overhead from soap is bigger than json.
Quickstart:
Create a new asmx Webservice in your .net webapp.
Include a reference to System.Web.
Decorate your webservice class with [ScriptService] and your method with [ScriptMethod(ResponseFormat = ResponseFormat.Json)]
[ScriptService]
public class WebService1 : System.Web.Services.WebService
{
[WebMethod]
[ScriptMethod(ResponseFormat = ResponseFormat.Json)]
public string HelloAndroid()
{
return "Hello Android";
}
}
(I think you have to add a reference to System.Web.Extension.dll which is available since .net 3.5).
Your webservice will still return XML (so you can use it with a soap client) unless you make a HTTPPost request with content-type "application/json".
use this code to contact the webservice from android:
private JSONObject sendJsonRequest(string host, int port,
String uri, JSONObject param)
throws ClientProtocolException, IOException, JSONException
{
HttpClient httpClient = new DefaultHttpClient();
HttpHost httpHost = new HttpHost(host, port);
HttpPost httpPost = new HttpPost(uri);
httpPost.addHeader("Content-Type", "application/json; charset=utf-8");
if (param != null)
{
HttpEntity bodyEntity = new StringEntity(param.toString(), "utf8");
httpPost.setEntity(bodyEntity);
}
HttpResponse response = httpClient.execute(httpHost, httpPost);
HttpEntity entity = response.getEntity();
String result = null;
if (entity != null) {
InputStream instream = entity.getContent();
BufferedReader reader = new BufferedReader(
new InputStreamReader(instream));
StringBuilder sb = new StringBuilder();
String line = null;
while ((line = reader.readLine()) != null)
sb.append(line + "\n");
result = sb.toString();
instream.close();
}
httpPost.abort();
return result != null ? new JSONObject(result) : null;
}
if your webservice methods looks like this:
[WebMethod]
[ScriptMethod(ResponseFormat = ResponseFormat.Json)]
public User GetUser(string name, int age)
{
return new User { Name = name, Age = age; }
}
You can call it this way from android:
public void getUser() {
// if you put a json object to the server
// the properties are automagically mapped to the methods' input parameters
JSONObject param = new JSONObject();
param.put("name", "John Doe");
param.put("age", 47);
JSONObject result = sendJsonRequest("server", 80,
"http://server:80/service1.asmx/GetUser", param);
if (result != null) {
JSONObject user = new JSONObject(result.getString("d"));
// .net webservices always return the result
// wrapped in a parameter named "d"
system.out.println(user.getString("name"));
system.out.println(user.getInt("age").toString());
}
}
Handling server exceptions on the client side:
Add this class to your project:
import org.json.JSONException;
import org.json.JSONObject;
public class JSONExceptionHelper {
private static final String KEY_MESSAGE = "Message";
private static final String KEY_EXCEPTIONTYPE = "ExceptionType";
private static final String KEY_STACKTRACE = "StackTrace";
public static boolean isException(JSONObject json) {
return json == null
? false
: json.has(KEY_MESSAGE) &&
json.has(KEY_EXCEPTIONTYPE) &&
json.has(KEY_STACKTRACE);
}
public static void ThrowJsonException(JSONObject json) throws JSONException {
String message = json.getString(KEY_MESSAGE);
String exceptiontype = json.getString(KEY_EXCEPTIONTYPE);
String stacktrace = json.getString(KEY_STACKTRACE);
StringBuilder sb = new StringBuilder();
sb.append(exceptiontype);
sb.append(": ");
sb.append(message);
sb.append(System.getProperty("line.separator"));
sb.append(stacktrace);
throw new JSONException(sb.toString());
}
}
Now replace the return statement from the sendJSONRequest with:
JSONObject json = result != null ? new JSONObject(result) : null
if (JSONExceptionHelper.isException(json))
JSONExceptionHelper.ThrowJsonException(json);
return json;
Please note: The exception is passed to the client only if connection comes from localhost.
Otherwise you get an http error 500 (or 501? I can't remember). You have to configure your IIS to send error 500 to the client.
Try it out and create a webservice that always throws an exception.

Sounds like a job for Web Services.
Start by creating a Web Service on the Windows web server, you can do this with ASP.NET (or maybe this might be more current).
On the Java side you can call the webservice and use the results that you get back. I think this question may help you get started on this side.

In case you have trouble writing web methods which return array of objects, you may want to refer here:
ksoap android web-service tutorial
Hope it helps.