WCF custom serialization - json

Question

I'm using .Net Framework WCF. This application receive json requests and response json string.
I would like to use my own serialization library for the serialization and deserialization actions.
In asp.net I used to do it in Global.asax file:
IJsonSerializer serializer = new Serializer();
GlobalConfiguration.Configuration.Formatters.Add(new CustomFormatter(serializer));
Here is my customer formatter class:
using System.Text;
using System;
using System.IO;
using System.Net.Http;
using System.Net.Http.Formatting;
using System.Net;
using System.Threading.Tasks;
namespace Test.Formatters
{
public class CustomFormatter: MediaTypeFormatter
{
private readonly IJsonSerializer _serializer;
public CustomFormatter(IJsonSerializer serializer)
{
_serializer = serializer;
SupportedMediaTypes.Add(new System.Net.Http.Headers.MediaTypeHeaderValue("application/json"));
SupportedMediaTypes.Add(new System.Net.Http.Headers.MediaTypeHeaderValue("text/json"));
SupportedMediaTypes.Add(new System.Net.Http.Headers.MediaTypeHeaderValue("application/xml"));
SupportedMediaTypes.Add(new System.Net.Http.Headers.MediaTypeHeaderValue("text/xml"));
SupportedEncodings.Add(Encoding.UTF8);
SupportedEncodings.Add(Encoding.Unicode);
}
public override bool CanReadType(Type type)
{
return true;
}
public override bool CanWriteType(Type type)
{
return true;
}
public override async Task<object> ReadFromStreamAsync(Type type, Stream readStream, HttpContent content, IFormatterLogger formatterLogger)
{
StreamReader reader = new StreamReader(readStream);
string text = await reader.ReadToEndAsync();
var serializedObj = _serializer.Deserialize(type, text);
return serializedObj;
}
public override async Task WriteToStreamAsync(Type type, object value, Stream writeStream, HttpContent content, TransportContext transportContext)
{
var serializedObj = _serializer.Serialize(value);
var encoding = Encoding.GetEncoding(content.Headers.ContentType.CharSet);
await writeStream.WriteAsync(encoding.GetBytes(serializedObj), 0, encoding.GetBytes(serializedObj).Length);
}
}
}
In .NetFramework WebAPI ReadFromStreamAsync and WriteToStreamAsync are triggered perfectly.
However, in WCF they are not triggered even though content-type is "application/json".
How can I handle WCF serialization by myself?