pass xml type parameter using jquery ajax to WCF Service

pass xml type parameter using jquery ajax to WCF Service

hi to all
I have to pass a collection of parameters using Jquery Ajax to Service method.One of my parameter is of xml type.How should i pass this collection.
Any help?

// this is my code here custom value is of xml type
var user = {
authtype: 1,
customvalue: "xml",
cityid: 1,
stateid: 1,
countryid: 1
};
var json = Sys.Serialization.JavaScriptSerializer.serialize(user);
$.ajax({
url: 'http://localhost:3162/VirtualService/Authentication.svc/RegisterConferenceUser',
type: 'Post',
contentType: 'application/json;charset=utf-8',
processData: true,
data: json,
success: function(response) {
alert(response);
},
failure: function(response) {
ShowInfoBar1(response);
}
});
}

This code is working for simple parameters but when i try to pass xml type no call to method is made