Pass JSON nested object to Post() method - C# WebAPI

Question

I have a C# WebAPI (I'm new to web API) which work fine as I can perform GET & POST request from Postman and from another C# program using HttpClient.

The POST method is "working" since I put a breakpoint into it to check if the code in it was triggered when I send a POST request, it is.

The "another C# program" is in charge of reading some data from a DB, serializing it (with JSON.Net) & sending it to the web API.

In the web API, I want to use the JSON serialized object (which include nested objects in it) to rebuild the same object I had before serializing and sending it. Every class used to create this object exists in the webAPI program.

I think that I just have to receive the JSON string and then deserialize it to my object, but I don't acheive to get this string, instead I get 'null' as the post parameter.

My code :

WebAPI configuration

public static class SHPC_APIConfig
{
    public static void Register(HttpConfiguration config)
    {
        // Web API routes
        config.MapHttpAttributeRoutes();

        config.Routes.MapHttpRoute(
            name: "ShPcAPI",
            routeTemplate: "api/{controller}/{id}",
            defaults: new {id = RouteParameter.Optional}
        );

        // Configure JSON formatter
        var jsonFormatter = config.Formatters.JsonFormatter;
        jsonFormatter.SerializerSettings.ContractResolver = new CamelCasePropertyNamesContractResolver();
    }
}

Controller

public class DataController : ApiController
{
    public string Get()
    {
        return "Hello world!";
    }

    public HttpResponseMessage Post([FromBody] string value)
    {
        var data = JsonConvert.DeserializeObject<Data>(value);
        Console.WriteLine(value != string.Empty ? "OK" : "KO");
        return new HttpResponseMessage(HttpStatusCode.OK);
    }
}

Performing a GET request works, I get the answer that I expect. Wherever I'm requesting from Postman or from my other C# program.

However, when I try to perform a POST request, the parameter value of the request is always null, wherever I'm requesting from Postman or from my other C# program.

Just use the correct type as a parameter. The JSON deserialisation should happen as part of the framework. Also, use WebApi 2 if possible, it's much nicer to define the routes using the attribute approach rather than registering them in config. — Steve
– Steve, Commented Aug 8, 2017 at 15:58
@DarrenYoung when you say the correct type, are you talking about the type "Data" that I want to deserialized the JSON to ? If it is, I've already try to expect Data as parameter of the Post() method instead of string, but it set a Data object with all default/null values... — Arnaud
– Arnaud, Commented Aug 8, 2017 at 16:02

Daniel Forero · Accepted Answer · 2017-08-08 18:21:45Z

2

In your WebApiConfig file into App_Start try to put this in the Register function:

var settings = 
GlobalConfiguration.Configuration.Formatters.JsonFormatter.SerializerSettings;

This will serialize all the responses in json.

edited Aug 8, 2017 at 18:21

answered Aug 8, 2017 at 16:01

Daniel Forero

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3 Comments

Arnaud Over a year ago

Thank you very much that works perfectly ! Do you know why my jsonFormatter var in the Register function doesn't do the job ?

Daniel Forero Over a year ago

it is because it maybe is trying to return a json into a XML response

Arnaud Over a year ago

Ok, thank you very much for your answer I was stuck in this for hours.

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