[json] HTTP 415 unsupported media type error when calling Web API 2 endpoint

I have an existing Web API 2 service and need to modify one of the methods to take a custom object as another parameter, currently the method has one parameter which is a simple string coming from the URL. After adding the custom object as a parameter I am now getting a 415 unsupported media type error when calling the service from a .NET windows app. Interestingly, I can successfully call this method using javascript and the jquery ajax method.

The Web API 2 service method looks like this:

<HttpPost>
<HttpGet>
<Route("{view}")>
Public Function GetResultsWithView(view As String, pPaging As Paging) As HttpResponseMessage
   Dim resp As New HttpResponseMessage
   Dim lstrFetchXml As String = String.Empty
   Dim lstrResults As String = String.Empty

   Try
      '... do some work here to generate xml string for the response
      '// write xml results to response
      resp.Content = New StringContent(lstrResults)
      resp.Content.Headers.ContentType.MediaType = "text/xml"
      resp.Headers.Add("Status-Message", "Query executed successfully")
      resp.StatusCode = HttpStatusCode.OK
   Catch ex As Exception
      resp.StatusCode = HttpStatusCode.InternalServerError
      resp.Headers.Add("Status-Message", String.Format("Error while retrieving results from view {0}: {1}", view, ex.Message))
   End Try
   Return resp
End Function

The method allows both POST and GET because the Paging object is optional. If I call this method with a GET request it works.

And the simple .NET client code calling the service looks like this:

Dim uri As String = BASE_URI + "fetch/someview"
Dim resp As HttpWebResponse
Dim sr As StreamReader
Dim lstrResponse As String
Dim reqStream As Stream
Dim bytData As Byte()
Dim req As HttpWebRequest = WebRequest.Create(uri)
Dim lstrPagingJSON As String
Dim lPaging As New Paging
Try
   lPaging.Page = 1
   lPaging.Count = 100
   lPaging.PagingCookie = ""
   req.Method = "POST"
   lstrPagingJSON = JsonSerializer(Of Paging)(lPaging)
   bytData = Encoding.UTF8.GetBytes(lstrPagingJSON)
   req.ContentLength = bytData.Length
   reqStream = req.GetRequestStream()
   reqStream.Write(bytData, 0, bytData.Length)
   reqStream.Close()
   req.ContentType = "application/json"

   resp = req.GetResponse()

   sr = New StreamReader(resp.GetResponseStream, Encoding.UTF8)
   lstrResponse = sr.ReadToEnd
   '// do something with the response here
Catch exweb As WebException
   txtOutput.AppendText("Error during request: " + exweb.Message)
Catch ex As Exception
   txtOutput.AppendText(String.Format("General error during request to {0}: {1}", uri, ex.Message))
End Try

The .NET client is running on the 4.5 framework and the service is on 4.5.2 framework. The error is thrown at the resp = req.GetResponse() line. Some things I tried already:

  • on the client, set the req.Accept value to "application/xml" or "text/xml"
  • in the service method, removed the line `resp.Content.Headers.ContentType.MediaType = "text/xml"
  • replace the XML response content with some static JSON, tried to rule out any problems with sending in JSON on the request and getting XML back on the response

So far I keep getting the same 415 error response no matter what I try.

I mentioned this works when called from javascript, here's my ajax call that is working:

$.ajax({
   headers: {},
   url: "api/fetch/someview",
   type: "POST",
   data: "{Count:100,Page:1,PagingCookie:\"\"}",
   contentType: "application/json; charset=utf-8",
   dataType: "xml",
   success: function (data) {
      alert("call succeeded");
   },
   failure: function (response) {
      alert("call failed");
   }
});

On the service side, there is nothing fancy going on with the route config or anything else, it's pretty much all out-of-the-box Web API 2. I know the routing is working, calls are being correctly routed to the method, they're not going somewhere else unexpectedly, so what am I missing in the .NET client? Any help is much appreciated!

--- UPDATE ---
I tried to create a completely new Web API service to rule out any possible issues with the existing service, I created a controller with a single method that takes a custom object as the parameter. I then tried calling that from the .NET client and got the same error. I also tried using WebClient instead of HttpWebRequest, but still get the same error. This is also something that previously worked for me with Web API (prior to Web API 2).

--- UPDATE ---
I also tried creating a new web app using Web API 1, when I call that with a POST my complex object parameter is now coming in null. I have another web service running Web API 1 and verified that I can still call that successfully with complex objects. Whatever my problem is, it appears to be something with the JSON passing between the client and server. I have checked the JSON I'm sending it and its valid, the object definition is also an exact match between the client and server so the JSON should be able to be parsed by the server.

The answer is


I also experienced this error.

I add into header Content-Type: application/json. Following the change, my submissions succeed!


I was failing to send a body on a DELETE that required one and was getting this message as a result.


I was trying to write a code that would work on both Mac and Windows. The code was working fine on Windows, but was giving the response as 'Unsupported Media Type' on Mac. Here is the code I used and the following line made the code work on Mac as well:

Request.AddHeader "Content-Type", "application/json"

Here is the snippet of my code:

Dim Client As New WebClient
Dim Request As New WebRequest
Dim Response As WebResponse
Dim Distance As String

Client.BaseUrl = "http://1.1.1.1:8080/config"
Request.AddHeader "Content-Type", "application/json" *** The line that made the code work on mac

Set Response = Client.Execute(Request)

In my case it is Asp.Net Core 3.1 API. I changed the HTTP GET method from public ActionResult GetValidationRulesForField( GetValidationRulesForFieldDto getValidationRulesForFieldDto) to public ActionResult GetValidationRulesForField([FromQuery] GetValidationRulesForFieldDto getValidationRulesForFieldDto) and its working.


I experienced this issue when calling my web api endpoint and solved it.

In my case it was an issue in the way the client was encoding the body content. I was not specifying the encoding or media type. Specifying them solved it.

Not specifying encoding type, caused 415 error:

var content = new StringContent(postData);
httpClient.PostAsync(uri, content);

Specifying the encoding and media type, success:

var content = new StringContent(postData, Encoding.UTF8, "application/json");
httpClient.PostAsync(uri, content);

Examples related to json

Use NSInteger as array index Uncaught SyntaxError: Unexpected end of JSON input at JSON.parse (<anonymous>) HTTP POST with Json on Body - Flutter/Dart Importing json file in TypeScript json.decoder.JSONDecodeError: Extra data: line 2 column 1 (char 190) Angular 5 Service to read local .json file How to import JSON File into a TypeScript file? Use Async/Await with Axios in React.js Uncaught SyntaxError: Unexpected token u in JSON at position 0 how to remove json object key and value.?

Examples related to vb.net

How to get parameter value for date/time column from empty MaskedTextBox HTTP 415 unsupported media type error when calling Web API 2 endpoint variable is not declared it may be inaccessible due to its protection level Differences Between vbLf, vbCrLf & vbCr Constants Simple working Example of json.net in VB.net How to open up a form from another form in VB.NET? Delete a row in DataGridView Control in VB.NET How to get cell value from DataGridView in VB.Net? Set default format of datetimepicker as dd-MM-yyyy How to configure SMTP settings in web.config

Examples related to asp.net-web-api

Entity Framework Core: A second operation started on this context before a previous operation completed FromBody string parameter is giving null How to read request body in an asp.net core webapi controller? JWT authentication for ASP.NET Web API Token based authentication in Web API without any user interface Web API optional parameters How do I get the raw request body from the Request.Content object using .net 4 api endpoint How to use a client certificate to authenticate and authorize in a Web API HTTP 415 unsupported media type error when calling Web API 2 endpoint The CodeDom provider type "Microsoft.CodeDom.Providers.DotNetCompilerPlatform.CSharpCodeProvider" could not be located

Examples related to asp.net-web-api2

CORS: credentials mode is 'include' FromBody string parameter is giving null Web API optional parameters HTTP 415 unsupported media type error when calling Web API 2 endpoint Asp.Net WebApi2 Enable CORS not working with AspNet.WebApi.Cors 5.2.3 How to implement oauth2 server in ASP.NET MVC 5 and WEB API 2 Pass multiple complex objects to a post/put Web API method Where can I find a NuGet package for upgrading to System.Web.Http v5.0.0.0? How to get base URL in Web API controller? No connection could be made because the target machine actively refused it?

Examples related to http-status-code-415

How can I get the status code from an http error in Axios? Curl to return http status code along with the response Job for httpd.service failed because the control process exited with error code. See "systemctl status httpd.service" and "journalctl -xe" for details How to deal with http status codes other than 200 in Angular 2 HTTP 415 unsupported media type error when calling Web API 2 endpoint AngularJS POST Fails: Response for preflight has invalid HTTP status code 404 Laravel - Return json along with http status code Swift Alamofire: How to get the HTTP response status code Spring Boot Rest Controller how to return different HTTP status codes? Http 415 Unsupported Media type error with JSON