How to return Xml rather than JSON from a Web API Action?

Question

How to configure the actions within a Web API Controller, to return XML rather than JSON?

I have an action which returns a UserProfile object which has XmlElement attributes:

[HttpGet]
        public UserProfile SearchByEmail(string siteName, string email)
        {
            var userProfile = this._profileFinderByEmail.Find(siteName, email);

            if (userProfile == null)
            {
                throw new HttpResponseException(HttpStatusCode.NotFound);
            }

            return userProfile;
        }

When when I run this action, it returns application/json rather than xml. How could I return xml?

Judging by Fiddler the request header that I was sending had the below Accept header key:

Accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8

that I expected it to return xml but it doesn't.

How to fix it?

I've also set the below value in the WebApiConfig class:

GlobalConfiguration.Configuration.Formatters.XmlFormatter.UseXmlSerializer = true;

Viewing from Chrome/Network tab, I can see the below error:

Status Code:406 Not Acceptable

are you sure , you interfaced your controller to 'ApiController'? — Sandy
– Sandy, Commented Mar 25, 2013 at 10:00

tpeczek · Accepted Answer · 2013-03-25 10:21:58Z

1

The header looks correct, so first you should check if the formatter is there. You can output all the registered formatters with following snippet (you can use it inside of your action method):

foreach (var formatter in GlobalConfiguration.Configuration.Formatters)
{
    System.Diagnostics.Debug.WriteLine(String.Format("{0}: {1}", formatter.GetType().Name, String.Join(", ", formatter.SupportedMediaTypes.Select(x=>x.MediaType))));
}

The results will be visible in Output window of Visual Studio (set Show output from to Debug). You should look for line like this:

XmlMediaTypeFormatter: application/xml, text/xml

If it is not there then it means that it was somehow removed and you need to find that part of code in your application. If it is there then it most probably means that DataContractSerializer wasn't able to serialize your entity (you can read more about the supported types here).

You also mentioned that you are using XmlElement attributes in your entity. By default XmlMediaTypeFormatter is using DataContractSerializer (as mentioned above) which will ignore those attributes. If you want to switch it to XmlSerializer you can use following code (for example in your Global.asax):

GlobalConfiguration.Configuration.Formatters.XmlFormatter.UseXmlSerializer = true;

Of course XmlSerializer has its own set of limitations which you need to be aware of.

answered Mar 25, 2013 at 10:21

tpeczek

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2 Comments

The Light Over a year ago

thanks. I've seen that XmlMediaTypeFormatter: application/xml, text/xml exists and JSON not. It's also strange that the debugger doesn't break in the global.ascx file.

tpeczek Over a year ago

@TheLight HTTP error 406 (Not Acceptable) means that no suitable formatter has been found (no formatter for such accept header or formatter is unable to format the entity). You can read more here.

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