How do I get ASP.NET Web API to return JSON instea

Question

Using the newer ASP.NET Web API, in Chrome I am seeing XML - how can I change it to request JSON so I can view it in the browser? I do believe it is just part of the request headers, am I correct in that?

Answer 1

I'm astonished to see so many replies requiring coding to change a single use case (GET) in one API instead of using a proper tool what has to be installed once and can be used for any API (own or 3rd party) and all use cases.

So the good answer is:

1. If you only want to request json or other content type install Requestly or a similar tool and modify the Accept header.
2. If you want to use POST too and have nicely formatted json, xml, etc. use a proper API testing extension like Postman or ARC.

Answer 2

Using RequestHeaderMapping works even better, because it also sets the Content-Type = application/json in the response header, which allows Firefox (with JSONView add-on) to format the response as JSON.

GlobalConfiguration.Configuration.Formatters.JsonFormatter.MediaTypeMappings
.Add(new System.Net.Http.Formatting.RequestHeaderMapping("Accept", 
                              "text/html",
                              StringComparison.InvariantCultureIgnoreCase,
                              true, 
                              "application/json"));

Answer 3

Have a look at content negotiation in the WebAPI. These (Part 1 & Part 2) wonderfully detailed and thorough blog posts explain how it works.

In short, you are right, and just need to set the Accept or Content-Type request headers. Given your Action isn't coded to return a specific format, you can set Accept: application/json.

Answer 4

I found the Chrome app "Advanced REST Client" excellent to work with REST services. You can set the Content-Type to application/json among other things: Advanced REST client

Answer 5

Most of the above answers makes perfect sense. Since you are seeing data being formatted in XML format ,that means XML formatter is applied,SO you can see JSON format just by removing the XMLFormatter from the HttpConfiguration parameter like

public static void Register(HttpConfiguration config)
        {
            config.Routes.MapHttpRoute(
                name: "DefaultApi",
                routeTemplate: "{controller}/{id}",
                defaults: new { id = RouteParameter.Optional }
            );                
            config.Formatters.Remove(config.Formatters.XmlFormatter);                
            config.EnableSystemDiagnosticsTracing();
        }

since JSON is the default format

Answer 6

I used a global action filter to remove Accept: application/xml when the User-Agent header contains "Chrome":

internal class RemoveXmlForGoogleChromeFilter : IActionFilter
{
    public bool AllowMultiple
    {
        get { return false; }
    }

    public async Task<HttpResponseMessage> ExecuteActionFilterAsync(
        HttpActionContext actionContext,
        CancellationToken cancellationToken,
        Func<Task<HttpResponseMessage>> continuation)
    {
        var userAgent = actionContext.Request.Headers.UserAgent.ToString();
        if (userAgent.Contains("Chrome"))
        {
            var acceptHeaders = actionContext.Request.Headers.Accept;
            var header =
                acceptHeaders.SingleOrDefault(
                    x => x.MediaType.Contains("application/xml"));
            acceptHeaders.Remove(header);
        }

        return await continuation();
    }
}

Seems to work.