Get request and accept json

iCalFormatter.cs

public class iCalFormatter
    : BufferedMediaTypeFormatter
{
    public iCalFormatter()
    {
        SupportedMediaTypes.Add(new MediaTypeHeaderValue("text/iCal"));
    }

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

    public override bool CanWriteType(Type type)
    {
        if (type == typeof(AppointmentModel))
        {
            return true;
        }
        else
        {
            Type enumerableType = typeof(IEnumerable<AppointmentModel>);
            return enumerableType.IsAssignableFrom(type);
        }
    }

    public override void WriteToStream(Type type, object value, Stream writeStream, System.Net.Http.HttpContent content)
    {
        using (var writer = new StreamWriter(writeStream))
        {
            writer.WriteLine("BEGIN:VCALENDAR");
            writer.WriteLine("VERSION:2.0");
            var appointments = value as IEnumerable<AppointmentModel>;
            if (appointments != null)
            {
                foreach (var appointment in appointments)
                {
                    WriteAppointment(appointment, writer);
                }
            }
            else
            {
                var singleAppointment = value as AppointmentModel;
                if (singleAppointment == null)
                {
                    throw new InvalidOperationException("Cannot serialize type");
                }
                WriteAppointment(singleAppointment, writer);
            }
            writer.WriteLine("END:VCALENDAR");
        }
        writeStream.Close();
    }

    private void WriteAppointment(AppointmentModel appointment, StreamWriter writer)
    {
        writer.WriteLine("BEGIN:VEVENT");
        writer.WriteLine("UID:" + appointment.Id);
        writer.WriteLine("DTSTART:" + string.Format("{0:yyyyMMddTHHmmssZ}", appointment.From));
        writer.WriteLine("DTEND:" + string.Format("{0:yyyyMMddTHHmmssZ}", appointment.Until));
        writer.WriteLine("SUMMARY:" + appointment.Title);
        writer.WriteLine("END:VEVENT");
    }
}

jsonresponse.json

[{"Id":1,"From":"2013-11-11T20:00:00","Until":"2013-11-11T21:00:00","Location":"Here","Title":"My title","Description":"My desc"}]

OutlookAgentMessageHandler.cs

public class OutlookAgentMessageHandler
    : DelegatingHandler
{
    protected override Task<HttpResponseMessage> SendAsync(HttpRequestMessage request, 
                                                          CancellationToken cancellationToken)
    {
        if (request.Headers.UserAgent.Any(x => x.Comment != null &&  x.Comment.Contains("Microsoft Outlook")))
        {
            request.Headers.Accept.Add(new System.Net.Http.Headers.MediaTypeWithQualityHeaderValue("text/iCal"));
        }
        return base.SendAsync(request, cancellationToken);
    }    
}

Request Appointments json

GET http://localhost:58250/api/appointments HTTP/1.1
User-Agent: Fiddler
Accept: application/json
Host: localhost:58250

Request Appointments xml

GET http://localhost:58250/api/appointments HTTP/1.1
User-Agent: Fiddler
Accept: application/xml
Host: localhost:58250

WebApiConfig.cs

public static class WebApiConfig
{
    public static void Register(HttpConfiguration config)
    {
        config.Routes.MapHttpRoute(
            name: "DefaultApi",
            routeTemplate: "api/{controller}/{id}",
            defaults: new { id = RouteParameter.Optional }
        );
       
       config.Formatters.Add(new iCalFormatter());
    }
}

WebApiConfigHandler.cs

public static class WebApiConfig
{
    public static void Register(HttpConfiguration config)
    {
        config.Routes.MapHttpRoute(
            name: "DefaultApi",
            routeTemplate: "api/{controller}/{id}",
            defaults: new { id = RouteParameter.Optional }
        );
           
        config.Formatters.Add(new iCalFormatter());
        config.MessageHandlers.Add(new OutlookAgentMessageHandler());
    }
}

xmlresponse.xml

<ArrayOfAppointmentModel xmlns:i="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://schemas.datacontract.org/2004/07/MvcApplication12"><AppointmentModel><Description>My desc</Description><From>2013-11-11T20:00:00</From><Id>1</Id><Location>Here</Location><Title>My title</Title><Until>2013-11-11T21:00:00</Until></AppointmentModel></ArrayOfAppointmentModel>