How to receive XmlDocument in MVC 4 Web Api?

I am posting XmlDocument to ApiController (from windows service, service is working fine, it is posting correct, I used it in wcf web API), but XML is always null, what am I doing wrong?

I can post some class, such in tutorials, or Get any data and everything will be ok, but I can't post XmlDocument.

public class XmlController : ApiController
{
    public void PostXml(XmlDocument xml)
    {
       // code
    }
}

I've found a solution:

We need to use inheritance to inherit MediaTypeFormatter

public class XmlMediaTypeFormatter : MediaTypeFormatter
{
    public XmlMediaTypeFormatter()
    {
        SupportedMediaTypes.Add(new MediaTypeHeaderValue("text/xml"));      
    }

    public override System.Threading.Tasks.Task<object> ReadFromStreamAsync(Type type, Stream stream,
         HttpContentHeaders contentHeaders,
         IFormatterLogger formatterLogger)
    {
        var taskCompletionSource = new TaskCompletionSource<object>();
        try
        {
            var memoryStream = new MemoryStream();
            stream.CopyTo(memoryStream);
            var s = System.Text.Encoding.UTF8.GetString(memoryStream.ToArray());

            XmlDocument xmlDoc = new XmlDocument();
            xmlDoc.LoadXml(s);

            taskCompletionSource.SetResult(xmlDoc);
        }
        catch (Exception e)
        {
            taskCompletionSource.SetException(e);
        }
        return taskCompletionSource.Task;
    }

    public override bool CanReadType(Type type)
    {
        return type == typeof(XmlDocument);
    }

    public override bool CanWriteType(Type type)
    {
        return false;
    }
}

Then register it in Global.asax:

GlobalConfiguration.Configuration.Formatters.Insert(0, new XmlMediaTypeFormatter());

Controller:

public HttpResponseMessage PostXml([FromBody] XmlDocument xml)
    {//code...}