Web API: Configure JSON serializer settings on action or controller level

Question

Overriding the default JSON serializer settings for web API on application level has been covered in a lot of SO threads. But how can I configure its settings on action level? For example, I might want to serialize using camelcase properties in one of my actions, but not in the others.

Could you not just craft the `HttpResponseMessage` manually setting the content to your desired json output? It's not as tidy as dealing with a global formatter but you can still create DRY helpers for dealing with these one off situations. — Phil Cooper, Jun 12 '17 at 12:12
The best approach would be to build an HTTP module and intercept each request and process as you need to for each different action. — Derek Hackett, Jun 12 '17 at 12:20
Would you consider an override per controller instead of per action? — Federico Dipuma, Jun 12 '17 at 12:24
@Johan I would tweak what they are doing in this example. If you need a detailed example for your use case just let me know. http://alexwolfthoughts.com/efficient-mvc-redirects-using-an-http-module/ — Derek Hackett, Jun 12 '17 at 15:53
@DerekHackett Thanks, I'll look in to it. Though Federico provided me with a good response too — Johan, Jun 12 '17 at 16:02

Federico Dipuma · Accepted Answer · 2018-10-13T17:42:08.713

Option 1 (quickest)

At action level you may always use a custom JsonSerializerSettings instance while using Json method:

public class MyController : ApiController
{
    public IHttpActionResult Get()
    {
        var settings = new JsonSerializerSettings
        {
            ContractResolver = new CamelCasePropertyNamesContractResolver()
        };
        var model = new MyModel();
        return Json(model, settings);
    }
}

Option 2 (controller level)

You may create a new IControllerConfiguration attribute which customizes the JsonFormatter:

public class CustomJsonAttribute : Attribute, IControllerConfiguration 
{
    public void Initialize(HttpControllerSettings controllerSettings, HttpControllerDescriptor controllerDescriptor)
    {
        var formatter = controllerSettings.Formatters.JsonFormatter;

        controllerSettings.Formatters.Remove(formatter);

        formatter = new JsonMediaTypeFormatter
        {
            SerializerSettings =
            {
                ContractResolver = new CamelCasePropertyNamesContractResolver()
            }
        };

        controllerSettings.Formatters.Insert(0, formatter);
    }
}

[CustomJson]
public class MyController : ApiController
{
    public IHttpActionResult Get()
    {
        var model = new MyModel();
        return Ok(model);
    }
}

do we need to instantiate a new formmater? can't we tweak the current instance or the change will be applied everywhere? — JobaDiniz, Jan 19 '18 at 17:43
@JobaDiniz as you stated, if you change properties of the original formatter, those changes will affect every other controller — Federico Dipuma, Jan 19 '18 at 17:47
Nice initialization of SerializerSettings! I didn't know about that C# feature. — gius, Feb 01 '18 at 10:38

score 15 · Answer 2 · answered Oct 11 '18 at 18:05

Here's an implementation of the above as Action Attribute:

public class CustomActionJsonFormatAttribute : ActionFilterAttribute
{
    public override void OnActionExecuted(HttpActionExecutedContext actionExecutedContext)
    {
        if (actionExecutedContext?.Response == null) return;

        var content = actionExecutedContext.Response.Content as ObjectContent;

        if (content?.Formatter is JsonMediaTypeFormatter)
        {
            var formatter = new JsonMediaTypeFormatter
            {
                SerializerSettings =
                {
                    ContractResolver = new CamelCasePropertyNamesContractResolver()
                }
            };

            actionExecutedContext.Response.Content = new ObjectContent(content.ObjectType, content.Value, formatter);
        }
    }
}

public class MyController : ApiController
{
    [CustomActionJsonFormat]
    public IHttpActionResult Get()
    {
        var model = new MyModel();
        return Ok(model);
    }
}

I used this code but I gave it a `Type ContractResolverType` property and then did `ContractResolver = (IContractResolver)Activator.CreateInstance(ContractResolverType)` so I don't have to create one of these for each contract resolver type. In use it looks like this: `[ActionContractResolver(ContractResolverType = typeof(DefaultContractResolver))]` — R. Salisbury, Mar 09 '21 at 19:11

score 0 · Answer 3 · answered Jun 25 '20 at 18:03

I needed to return a 404 status error code alongside a json object with error details. I solved it using WebApi.Content with a new new JsonMediaTypeFormatter.

public class MyController : ApiController
{
    public IHttpActionResult Get()
    {
        // Configure new Json formatter
        var formatter = new JsonMediaTypeFormatter
        {
            SerializerSettings =
            {
                TypeNameHandling = TypeNameHandling.None,
                PreserveReferencesHandling = PreserveReferencesHandling.None,
                Culture = CultureInfo.InvariantCulture,
                Formatting = Formatting.Indented,
                NullValueHandling = NullValueHandling.Ignore
            }
        };

        try
        {
            var model = new MyModel();
            return Content(HttpStatusCode.OK, model, formatter);
        }
        catch (Exception err)
        {
            var errorDto = GetErrorDto(HttpStatusCode.NotFound, $"{err.Message}");
            return Content(HttpStatusCode.NotFound, errorDto, formatter);
        }
    }
}

Web API: Configure JSON serializer settings on action or controller level

3 Answers3

Option 1 (quickest)

Option 2 (controller level)

Linked