Post JSON string to WEB API

Question

I have an ASP.NET WEB-API 2 app witch needs to have a POST method that accepts a JOSN string with unknown structure from javascript.
I enabled cors and GET methods works fine, however when sending JSON from the client the api's method parameter is always null.
This is my api method:

//parameters i tried:
//[FromBody]string model
//[FromBody]dynamic model
//dynamic model
public HttpResponseMessage Post(string model)
{
 return new HttpResponseMessage()
 {
 Content = new StringContent("POST: Test message: " + model)
 };
}

and my client method:

function sendRequest()
{
 var Test = {"Name":"some name"};
 var method = $('#method').val();
 $.ajax({
 type: method,
 url: serviceUrl,
 contentType: 'application/json; charset=utf-8',
 data: JSON.stringify(Test) 
 }).done(function (data)
 {
 $('#value1').text(data);
 }).error(function (jqXHR, textStatus, errorThrown)
 {
 $('#value1').text(jqXHR.responseText || textStatus);
 });
}

So the question is how can I post an unknown JSON string from javascript and accept it as a string in my api method?

• Rajshekar Reddy: try data: {model :JSON.stringify(Test)}
• Yoav: this gives me a Response to preflight request doesn't pass access control check: No 'Access-Control-Allow-Origin' header is present on the requested resource error message
• Marcus Höglund: Don't JSON.stringify. Use Data: {value: Test} and in your controller ([FromBody]string Test). That should return a string.
• Alex Nguyen: Don't use JOSN contentType. Just post a string with json format then use JsonConvert.DeserializeObject to convert it to your expected object.
• Yoav: @MarcusH tried but I still get a null value

Answer 1

I edited your code and it works well.

A [FromBody] attribute specifies that an action parameter comes only from the entity body of the incoming HTTPRequestMessage.

public class TestApiController : ApiController
 {
 // POST api/<controller>
 [HttpPost]
 public HttpResponseMessage Post([FromBody]string value)
 {
 return new HttpResponseMessage()
 {
 Content = new StringContent("POST: Test message: " + value)
 };
 }
 }
function sendRequest() {
 var Test = { "Name": "some name" };
 $.ajax({
 type: "POST",
 url: "api/TestApi",
 data: { '': JSON.stringify(Test) }
 }).done(function (data) {
 alert(data);
 }).error(function (jqXHR, textStatus, errorThrown) {
 alert(jqXHR.responseText || textStatus);
 });
}

• Christoph Adamakis: I tried your suggestion and It works. But I want to find an explanation. The link you provided contains malware
• Alex Nguyen: @ChristophAdamakis : learn.microsoft.com/en-us/aspnet/web-api/overview/…

Answer 2

Either treat the POST request as a generic HTTP request, and manually parse the body:

public async Task<HttpResponseMessage> Post(HttpRequestMessage request)
{
 var jsonString = await request.Content.ReadAsStringAsync();
 // deserialize the string, or do other stuff
 return new HttpResponseMessage(HttpStatusCode.OK);
}

Or use a generic JToken, and let the serializer do the rest:

public HttpResponseMessage Post([FromBody] JToken model)
{
 DoStuff(model);
 var myField = model["fieldName"];
 return new HttpResponseMessage(HttpStatusCode.OK);
}

Notes: this way you do not need to alter client-side code, because you are still POSTing json data, not a generic string, which is semantically the right choice if you expect your client to post serialized JSON objects.

References:

http://bizcoder.com/posting-raw-json-to-web-api