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Returning the correct format is done by the media-type formatter. As others mentioned, you can do this in the WebApiConfig class:

public static class WebApiConfig { public static void Register(HttpConfiguration config) { ... // Configure Web API to return JSON config.Formatters.JsonFormatter .SupportedMediaTypes.Add(new System.Net.Http.Headers.MediaTypeHeaderValue("text/html")); ... } } 

For more, check:

• Media Formatters in ASP.NET Web API 2.
• Content Negotiation in ASP.NET Web API.

In case your actions are returning XML and you need just a specific method to return JSON, you can then use an ActionFilterAttribute and apply it to that specific action.

Filter attribute:

public class JsonOutputAttribute : ActionFilterAttribute { public override void OnActionExecuted(HttpActionExecutedContext actionExecutedContext) { ObjectContent content = actionExecutedContext.Response.Content as ObjectContent; var value = content.Value; Type targetType = actionExecutedContext.Response.Content.GetType().GetGenericArguments()[0]; var httpResponseMsg = new HttpResponseMessage { StatusCode = HttpStatusCode.OK, RequestMessage = actionExecutedContext.Request, Content = new ObjectContent(targetType, value, new JsonMediaTypeFormatter(), (string)null) }; actionExecutedContext.Response = httpResponseMsg; base.OnActionExecuted(actionExecutedContext); } } 

Applying to action:

[JsonOutput] public IEnumerable<Person> GetPersons() { return _repository.AllPersons(); // the returned output will be in JSON } 

Note that you can omit the word Attribute on the action decoration and use just [JsonOutput] instead of [JsonOutputAttribute].

Returning the correct format is done by the media-type formatter. As others mentioned, you can do this in the WebApiConfig class:

public static class WebApiConfig { public static void Register(HttpConfiguration config) { ... // Configure Web API to return JSON config.Formatters.JsonFormatter .SupportedMediaTypes.Add(new System.Net.Http.Headers.MediaTypeHeaderValue("text/html")); ... } } 

For more, check:

• Media Formatters in ASP.NET Web API 2.
• Content Negotiation in ASP.NET Web API.

In case your actions are returning XML (which is the case by default) and you need just a specific method to return JSON, you can then use an ActionFilterAttribute and apply it to that specific action.

Filter attribute:

public class JsonOutputAttribute : ActionFilterAttribute { public override void OnActionExecuted(HttpActionExecutedContext actionExecutedContext) { ObjectContent content = actionExecutedContext.Response.Content as ObjectContent; var value = content.Value; Type targetType = actionExecutedContext.Response.Content.GetType().GetGenericArguments()[0]; var httpResponseMsg = new HttpResponseMessage { StatusCode = HttpStatusCode.OK, RequestMessage = actionExecutedContext.Request, Content = new ObjectContent(targetType, value, new JsonMediaTypeFormatter(), (string)null) }; actionExecutedContext.Response = httpResponseMsg; base.OnActionExecuted(actionExecutedContext); } } 

Applying to action:

[JsonOutput] public IEnumerable<Person> GetPersons() { return _repository.AllPersons(); // the returned output will be in JSON } 

Note that you can omit the word Attribute on the action decoration and use just [JsonOutput] instead of [JsonOutputAttribute].

Returning the correct format is done by the media-type formatter. As others mentioned, you can do this in the WebApiConfig class:

public static class WebApiConfig { public static void Register(HttpConfiguration config) { ... // Configure Web API to return JSON config.Formatters.JsonFormatter .SupportedMediaTypes.Add(new System.Net.Http.Headers.MediaTypeHeaderValue("text/html")); ... } } 

For more, check:

• Media Formatters in ASP.NET Web API 2.
• Content Negotiation in ASP.NET Web API.

Returning the correct format is done by the media-type formatter. As others mentioned, you can do this in the WebApiConfig class:

public static class WebApiConfig { public static void Register(HttpConfiguration config) { ... // Configure Web API to return JSON config.Formatters.JsonFormatter .SupportedMediaTypes.Add(new System.Net.Http.Headers.MediaTypeHeaderValue("text/html")); ... } } 

For more, check:

• Media Formatters in ASP.NET Web API 2.
• Content Negotiation in ASP.NET Web API.

In case your actions are returning XML and you need just a specific method to return JSON, you can then use an ActionFilterAttribute and apply it to that specific action.

Filter attribute:

public class JsonOutputAttribute : ActionFilterAttribute { public override void OnActionExecuted(HttpActionExecutedContext actionExecutedContext) { ObjectContent content = actionExecutedContext.Response.Content as ObjectContent; var value = content.Value; Type targetType = actionExecutedContext.Response.Content.GetType().GetGenericArguments()[0]; var httpResponseMsg = new HttpResponseMessage { StatusCode = HttpStatusCode.OK, RequestMessage = actionExecutedContext.Request, Content = new ObjectContent(targetType, value, new JsonMediaTypeFormatter(), (string)null) }; actionExecutedContext.Response = httpResponseMsg; base.OnActionExecuted(actionExecutedContext); } } 

Applying to action:

[JsonOutput] public IEnumerable<Person> GetPersons() { return _repository.AllPersons(); // the returned output will be in JSON } 

Note that you can omit the word Attribute on the action decoration and use just [JsonOutput] instead of [JsonOutputAttribute].

Returning the correct format is done by the media-type formatter. As others mentioned, you can do this in the WebApiConfig class:

public static class WebApiConfig { public static void Register(HttpConfiguration config) { ... // Configure Web API to return JSON config.Formatters.JsonFormatter .SupportedMediaTypes.Add(new System.Net.Http.Headers.MediaTypeHeaderValue("text/html")); ... } } 

Read more about Media Formatters in ASP.NET Web API 2.

Returning the correct format is done by the media-type formatter. As others mentioned, you can do this in the WebApiConfig class:

public static class WebApiConfig { public static void Register(HttpConfiguration config) { ... // Configure Web API to return JSON config.Formatters.JsonFormatter .SupportedMediaTypes.Add(new System.Net.Http.Headers.MediaTypeHeaderValue("text/html")); ... } } 

For more, check:

• Media Formatters in ASP.NET Web API 2.
• Content Negotiation in ASP.NET Web API.