Return "Raw" JSON in ASP.NET Core 2.0 Web API

Return raw json in ASP.NET Core 2.0 Web Api

And of course a few minutes after posting the question I stumble upon a solution :)

Just return Content with the content type application/json...

return Content("{ \"name\":\"John\", \"age\":31, \"city\":\"New York\" }", "application/json");

ASP.NET Core v2 (2015) MVC : How to get raw JSON bound to a string without a type?

The following works in .net core 1.x, but not in .net core 2.x.

As I commented, the solution is to use [FromBody]dynamic data as my parameter list, using dynamic instead of string, and I will receive a JObject.

Caution: If your architecture calls for a single WebApi server to be equally fluent in producing XML and JSON, depending on content-type header entries, this kind of direct-JSON-consumption strategy can backfire on you. (Supporting both XML and JSON on the same service is possible with sufficient work, but then you're taking stuff that was further UP the MVC asset pipeline and moving it down into your controller methods, which turns out to be against the spirit of MVC, where models come to you as POCOs already parsed.)

Once you convert to a string inside the method, converting the incoming JObject (Newtonsoft.JSON in memory data type for JSON) to a string.

Found at other answer here.

Sample code, thanks to Jeson Martajaya:

With dynamic:

[HttpPost]
public System.Net.Http.HttpResponseMessage Post([FromBody]dynamic value)
{
   //...
}

Sample code with JObject:

[HttpPost]
public System.Net.Http.HttpResponseMessage Post([FromBody]Newtonsoft.Json.Linq.JObject value)
{
   //...
}

ASP.NET Core return JSON with status code

The most basic version responding with a JsonResult is:

// GET: api/authors
[HttpGet]
public JsonResult Get()
{
    return Json(_authorRepository.List());
}

However, this isn't going to help with your issue because you can't explicitly deal with your own response code.

The way to get control over the status results, is you need to return a ActionResult which is where you can then take advantage of the StatusCodeResult type.

for example:

// GET: api/authors/search?namelike=foo
[HttpGet("Search")]
public IActionResult Search(string namelike)
{
    var result = _authorRepository.GetByNameSubstring(namelike);
    if (!result.Any())
    {
        return NotFound(namelike);
    }
    return Ok(result);
}

Note both of these above examples came from a great guide available from Microsoft Documentation: Formatting Response Data

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Extra Stuff

The issue I come across quite often is that I wanted more granular control over my WebAPI rather than just go with the defaults configuration from the "New Project" template in VS.

Let's make sure you have some of the basics down...

Step 1: Configure your Service

In order to get your ASP.NET Core WebAPI to respond with a JSON Serialized Object along full control of the status code, you should start off by making sure that you have included the AddMvc() service in your ConfigureServices method usually found in Startup.cs.

It's important to note thatAddMvc() will automatically include the Input/Output Formatter for JSON along with responding to other request types.

If your project requires full control and you want to strictly define your services, such as how your WebAPI will behave to various request types including application/json and not respond to other request types (such as a standard browser request), you can define it manually with the following code:

public void ConfigureServices(IServiceCollection services)
{
    // Build a customized MVC implementation, without using the default AddMvc(), instead use AddMvcCore().
    // https://github.com/aspnet/Mvc/blob/dev/src/Microsoft.AspNetCore.Mvc/MvcServiceCollectionExtensions.cs

    services
        .AddMvcCore(options =>
        {
            options.RequireHttpsPermanent = true; // does not affect api requests
            options.RespectBrowserAcceptHeader = true; // false by default
            //options.OutputFormatters.RemoveType<HttpNoContentOutputFormatter>();

            //remove these two below, but added so you know where to place them...
            options.OutputFormatters.Add(new YourCustomOutputFormatter()); 
            options.InputFormatters.Add(new YourCustomInputFormatter());
        })
        //.AddApiExplorer()
        //.AddAuthorization()
        .AddFormatterMappings()
        //.AddCacheTagHelper()
        //.AddDataAnnotations()
        //.AddCors()
        .AddJsonFormatters(); // JSON, or you can build your own custom one (above)
}

You will notice that I have also included a way for you to add your own custom Input/Output formatters, in the event you may want to respond to another serialization format (protobuf, thrift, etc).

The chunk of code above is mostly a duplicate of the AddMvc() method. However, we are implementing each "default" service on our own by defining each and every service instead of going with the pre-shipped one with the template. I have added the repository link in the code block, or you can check out AddMvc() from the GitHub repository..

Note that there are some guides that will try to solve this by "undoing" the defaults, rather than just not implementing it in the first place... If you factor in that we're now working with Open Source, this is redundant work, bad code and frankly an old habit that will disappear soon.

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Step 2: Create a Controller

I'm going to show you a really straight-forward one just to get your question sorted.

public class FooController
{
    [HttpPost]
    public async Task<IActionResult> Create([FromBody] Object item)
    {
        if (item == null) return BadRequest();

        var newItem = new Object(); // create the object to return
        if (newItem != null) return Ok(newItem);

        else return NotFound();
    }
}

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Step 3: Check your Content-Type and Accept

You need to make sure that your Content-Type and Accept headers in your request are set properly. In your case (JSON), you will want to set it up to be application/json.

If you want your WebAPI to respond as JSON as default, regardless of what the request header is specifying you can do that in a couple ways.

Way 1
As shown in the article I recommended earlier (Formatting Response Data) you could force a particular format at the Controller/Action level. I personally don't like this approach... but here it is for completeness:

Forcing a Particular Format If you would like to restrict the response formats for a specific action you can, you can apply the
[Produces] filter. The [Produces] filter specifies the response
formats for a specific action (or controller). Like most Filters, this
can be applied at the action, controller, or global scope.

[Produces("application/json")]
public class AuthorsController

The [Produces] filter will force all actions within the
AuthorsController to return JSON-formatted responses, even if other
formatters were configured for the application and the client provided
an Accept header requesting a different, available format.

Way 2
My preferred method is for the WebAPI to respond to all requests with the format requested. However, in the event that it doesn't accept the requested format, then fall-back to a default (ie. JSON)

First, you'll need to register that in your options (we need to rework the default behavior, as noted earlier)

options.RespectBrowserAcceptHeader = true; // false by default

Finally, by simply re-ordering the list of the formatters that were defined in the services builder, the web host will default to the formatter you position at the top of the list (ie position 0).

More information can be found in this .NET Web Development and Tools Blog entry

How to force ASP.NET Web API to always return JSON?

Supporting only JSON in ASP.NET Web API – THE RIGHT WAY

Replace IContentNegotiator with JsonContentNegotiator:

var jsonFormatter = new JsonMediaTypeFormatter();
//optional: set serializer settings here
config.Services.Replace(typeof(IContentNegotiator), new JsonContentNegotiator(jsonFormatter));

JsonContentNegotiator implementation:

public class JsonContentNegotiator : IContentNegotiator
{
    private readonly JsonMediaTypeFormatter _jsonFormatter;

    public JsonContentNegotiator(JsonMediaTypeFormatter formatter) 
    {
        _jsonFormatter = formatter;    
    }

    public ContentNegotiationResult Negotiate(
            Type type, 
            HttpRequestMessage request, 
            IEnumerable<MediaTypeFormatter> formatters)
    {
        return new ContentNegotiationResult(
            _jsonFormatter, 
            new MediaTypeHeaderValue("application/json"));
    }
}

.NET Core 3.1 WebApi - Passthrough JSON response from another WebApi

You need to do this:

return Content(result, "application/json");

How to return a Json from a .Net Core Web API?

Add this attribute to your controller class:

[Produces("application/json")]

So it becomes:

[Produces("application/json")]
public class YourController: Controller {

   [HttpGet]
   public IEnumerable<string> Get()
   {
       return new string[] { "value1", "value2" };
   }
}

That should be enough, otherwise I believe the default is XML (unless the client explicitly asks for JSON using the Accept HTTP header).

.NET Core 1.0 Web Api processing request body as JSON when content-type is text/plain

I made it work by adding the text/plain content-type to the JsonInputFormatter in Startup.cs ConfigureServices() method, like so:

        public void ConfigureServices(IServiceCollection services)
        {
            services.AddMvc(config =>
            {
                foreach (var formatter in config.InputFormatters)
                {
                    if (formatter.GetType() == typeof(JsonInputFormatter))
                        ((JsonInputFormatter)formatter).SupportedMediaTypes.Add(
                            MediaTypeHeaderValue.Parse("text/plain"));
                }
            });
            ...
         }

Edit: I made a seed project for the SNS client lambda, that parses the message and confirms the subscription out the box.

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