public partial class TraditionalServices : UserControl
{
    private ServiceClient service;
    public TraditionalServices()
    {
        InitializeComponent();

        service = new ServiceClient();
        service.GetDateCompleted += new EventHandler<GetDateCompletedEventArgs>(OnGetDateCompleted);
        service.GetEmployeeCompleted += new EventHandler<GetEmployeeCompletedEventArgs>(OnGetEmployeeCompleted);

        Loaded += new RoutedEventHandler(OnLoaded);
    }

    void OnLoaded(object sender, RoutedEventArgs e)
    {
        service.GetDateAsync();
    }

    void OnGetEmployeeCompleted(object sender, GetEmployeeCompletedEventArgs e)
    {

    }

    void OnGetDateCompleted(object sender, GetDateCompletedEventArgs e)
    {

    }
}

service.GetDateTime(value =>
{
    string currentDateTime = value.ToString();
});

public void GetDateTime(Action<DateTime> value)
{
    service.GetDateAsync(value);
}

public partial class MainPage : UserControl
{
Helpers.ServiceHelper service;
public MainPage()
{
   InitializeComponent();

   service = Helpers.ServiceHelper.Instance;

   service.GetDateTime(value =>
   {
       string currentDateTime = value.ToString();
   });

   service.GetEmployee(value =>
   {
       ListBox listbox = new ListBox();
       listbox.ItemsSource = value;
       LayoutRoot.Children.Add(listbox);
   });

   service.DoStuff(() =>
   {
       // do stuff done
   });
}
}

public class ServiceHelper
{
private static ServiceHelper instance = new ServiceHelper();
public static ServiceHelper Instance { get { return instance; } }

private ServiceClient service;

private ServiceHelper()
{
   service = new ServiceClient();
   service.GetDateCompleted += new EventHandler<GetDateCompletedEventArgs>(OnGetDateCompleted);
   service.GetEmployeeCompleted += new EventHandler<GetEmployeeCompletedEventArgs>(OnGetEmployeeCompleted);
   service.AddCompleted += new EventHandler<AddCompletedEventArgs>(OnAddCompleted);
   service.DoStuffCompleted += new EventHandler<System.ComponentModel.AsyncCompletedEventArgs>(OnDoStuffCompleted);
}

void OnDoStuffCompleted(object sender, System.ComponentModel.AsyncCompletedEventArgs e)
{
   if (e.Error == null)
   {
       Action action = (Action)e.UserState;
       action();
   }
}

void OnAddCompleted(object sender, AddCompletedEventArgs e)
{
   if (e.Error == null)
   {
       Action<int> action = (Action<int>)e.UserState;
       action(e.Result);
   }
}

void OnGetEmployeeCompleted(object sender, GetEmployeeCompletedEventArgs e)
{
   if (e.Error == null)
   {
       Action<ObservableCollection<Employee>> action = (Action<ObservableCollection<Employee>>)e.UserState;
       action(e.Result);
   }
}

void OnGetDateCompleted(object sender, GetDateCompletedEventArgs e)
{
   if (e.Error == null)
   {
       Action<DateTime> action = (Action<DateTime>)e.UserState;
       action(e.Result);
   }
}

public void GetDateTime(Action<DateTime> value)
{
   service.GetDateAsync(value);
}

public void GetEmployee(Action<ObservableCollection<Employee>> value)
{
   service.GetEmployeeAsync(value);
}

public void Add(AddArguments args, Action<int> value)
{
   service.AddAsync(args.Operand1, args.Operand2, value);
}

public void DoStuff(Action value)
{
   service.DoStuffAsync(value);
}

public class AddArguments
{
   public int Operand1 { get; set; }
   public int Operand2 { get; set; }
}
}