JsonWriter and contentType: "application/json; charset=utf-8",

[andycramb]

I am trying to call a .NET web service using a JsonWriter but i believe its blowing up as the content type is

application/x-www-form-urlencoded; charset=UTF-8

where I need it to be

application/json; charset=utf-8

My writer is set up like this with encode set to false but this does not do the trick
Can anyone give me a steer on how to change the content type

  var writer = new Ext.data.JsonWriter({
        encode          : false
        ,writeAllFields  : false
    });

Thanks