Datactontract serializer with json

gistfile1.cs

public class UploadServceClient
{
    RestClient RestClient;

    public UploadServceClient()
    {
        RestClient = new RestClient("http://localhost/MyService");
    }


    public MyResponseMessage CallMyEndpoint(MyRequestMessage myRequest)
    {
        string body = HackyBodyCreation(myRequest);


        var restRequest = new RestRequest(Method.POST);
        restRequest.RequestFormat = DataFormat.Xml;
        restRequest.Resource = "Myoperation";
        restRequest.AddParameter("application/xml", body, ParameterType.RequestBody);
        var restResponse = RestClient.Execute<MyResponseMessage>(restRequest);
        return restResponse.Data;
    }

    private string HackyBodyCreation(MyRequestMessage myRequest)
    {
        var builder = new StringBuilder();
        var serializer = new DataContractSerializer(typeof(MyRequestMessage));
        var xmlWriter = XmlWriter.Create(builder);
        serializer.WriteObject(xmlWriter,myRequest);
        xmlWriter.Close();

        return builder.ToString().Replace("<?xml version=\"1.0\" encoding=\"utf-16\"?>","");
    }
}