pass the object of class to web service not working in client side

hello guys,
  i have one web service and some methods with objects parameter of some custom class. and now  client application need to  create objects of custom class and call our web service methods . like this
 For example class:
public class AuthenticationHeader
{
    public AuthenticationHeader()
    {
        //
        // TODO: Add constructor logic here
        //
    }
    public string AuthenticationName = "";
    public string AuthenticationPassword = "";
 }
this is the class and in web service i am calling 
 MemberWebService.asmx
 public string HelloWorld(AuthenticationHeader objAuthenticationHeader) {
        return "Hel ...