The Unit Test of Silverlight Applications with Asynchronous Service Callbacks

using System;
using SilverlightApplication.Utilities;
using SilverlightApplication.StudentService;
using System.Collections.Generic;
using SilverlightApplication.Models;

namespace SilverlightApplication.ViewModels
{
    public class MainPageViewModel : ViewModelBase
    {
        // Public properties
        private List<Student> studentList = null;
        public List<Student> StudentList
        {
            get { return studentList; }
            private set
            {
                studentList = value;
                NotifyPropertyChanged("StudentList");
            }
        }

        // Public commands
        public RelayCommand GetStudentWCFCommand { get; private set; }
        private void GetStudentWCF()
        {
            StudentModel model = new StudentModel();
            model.GetStudents(10, (s, r) =>
            {
                StudentList = (List<Student>)r.Result;

                // This is used for unit testing
                // It has no effect to the normal program flow.
                InformCallbackCompleted();
            });
        }

        public RelayCommand GetStudentWCFWrongMethodCommand { get; private set; }
        private void GetStudentWCFWrongMethod()
        {
            StudentModel model = new StudentModel();
            model.GetStudentsWithError(10, (s, r) =>
            {
                StudentList = (List<Student>)r.Result;

                // This is used for unit testing
                // It has no effect to the normal program flow.
                InformCallbackCompleted();
            });
        }

        // Commands should be initiated in this method
        private void WireCommands()
        {
            GetStudentWCFCommand = new RelayCommand(GetStudentWCF);
            GetStudentWCFCommand.IsEnabled = true;

            GetStudentWCFWrongMethodCommand = new RelayCommand(GetStudentWCFWrongMethod);
            GetStudentWCFWrongMethodCommand.IsEnabled = true;
        }

        // Constructor
        public MainPageViewModel() : base()
        {
            WireCommands();
        }
    }
}