Silverlight Super Tabs Interface (using View Model / MVVM)

using System;
using System.Linq;
using System.Collections.Generic;
using System.Text;
using System.Windows.Data;
using System.ComponentModel;
using System.Collections.ObjectModel;
using System.Windows.Input;

namespace SimpleAttendance
{
    public class OverviewModel : INotifyPropertyChanged
    {
        public OverviewModel()
        {
            // Set the command properties
            ComputeTotalsCommand = new DelegateCommand(ComputeTotals, CanComputeTotals);
        }

        #region ComputeTotalsCommand
        public ICommand ComputeTotalsCommand { get; set; }
        public void ComputeTotals(object param)
        {
            if (!(DesignerProperties.IsInDesignTool))
            {
                LoadData();
            }
        }

        private bool CanComputeTotals(object param)
        {
            return true;
        }
        #endregion

        // Operations

        #region LoadData
        public void LoadData()
        {
            bool hasKeys = false;
            foreach (var item in SterlingService.Current.Database.Query<Student, int>())
            {
                hasKeys = true;
                break;
            }

            if (hasKeys)
            {
                // Clear All Collections
                Students.Clear();
                Enrollments.Clear();
                colAttendance.Clear();
                colStudentOverview.Clear();

                // Get the data
                foreach (var item in SterlingService.Current.Database.Query<Student, int>())
                {
                    Students.Add(item.LazyValue.Value);
                }

                foreach (var item in SterlingService.Current.Database.Query<Enrollment, int>())
                {
                    Enrollments.Add(item.LazyValue.Value);
                }

                foreach (var item in SterlingService.Current.Database.Query<Attendance, string>())
                {
                    colAttendance.Add(item.LazyValue.Value);
                }


                // Create the Query
                var result = from Student in Students
                             select new StudentOverview
                             {
                                 StudentId = Student.StudentId,
                                 Name = Student.Name,
                                 P = (from objEnrollment in Enrollments
                                      from objAttendance in colAttendance
                                      where objEnrollment.StudentId == Student.StudentId
                                      where objEnrollment.EnrollmentId == objAttendance.EnrollmentId
                                      where objAttendance.AttendanceStatus == "P"
                                      select objAttendance).Count(),
                                 T = (from objEnrollment in Enrollments
                                      from objAttendance in colAttendance
                                      where objEnrollment.StudentId == Student.StudentId
                                      where objEnrollment.EnrollmentId == objAttendance.EnrollmentId
                                      where objAttendance.AttendanceStatus == "T"
                                      select objAttendance).Count(),
                                 E = (from objEnrollment in Enrollments
                                      from objAttendance in colAttendance
                                      where objEnrollment.StudentId == Student.StudentId
                                      where objEnrollment.EnrollmentId == objAttendance.EnrollmentId
                                      where objAttendance.AttendanceStatus == "E"
                                      select objAttendance).Count(),
                                 U = (from objEnrollment in Enrollments
                                      from objAttendance in colAttendance
                                      where objEnrollment.StudentId == Student.StudentId
                                      where objEnrollment.EnrollmentId == objAttendance.EnrollmentId
                                      where objAttendance.AttendanceStatus == "U"
                                      select objAttendance).Count(),
                             };

                // Fill the final Collection
                foreach (var Student in result)
                {
                    colStudentOverview.Add(Student);
                }
            }
        }
        #endregion

        // Properties (View Models)

        #region MainPageModelVM
        private MainPageModel _MainPageModelVM;
        public MainPageModel MainPageModelVM
        {
            get { return _MainPageModelVM; }
            set
            {
                if (MainPageModelVM == value)
                {
                    return;
                }
                _MainPageModelVM = value;
                this.NotifyPropertyChanged("MainPageModelVM");
            }
        }
        #endregion

        // Collections

        #region colStudentOverview
        private ObservableCollection<StudentOverview> _colStudentOverview
            = new ObservableCollection<StudentOverview>();
        public ObservableCollection<StudentOverview> colStudentOverview
        {
            get { return _colStudentOverview; }
            private set
            {
                if (colStudentOverview == value)
                {
                    return;
                }
                _colStudentOverview = value;
                this.NotifyPropertyChanged("colStudentOverview");
            }
        }
        #endregion

        #region Students
        private ObservableCollection<Student> _Students
            = new ObservableCollection<Student>();
        public ObservableCollection<Student> Students
        {
            get { return _Students; }
            private set
            {
                if (Students == value)
                {
                    return;
                }
                _Students = value;
                this.NotifyPropertyChanged("Students");
            }
        }
        #endregion

        #region Enrollments
        private ObservableCollection<Enrollment> _Enrollments
            = new ObservableCollection<Enrollment>();
        public ObservableCollection<Enrollment> Enrollments
        {
            get { return _Enrollments; }
            private set
            {
                if (Enrollments == value)
                {
                    return;
                }
                _Enrollments = value;
                this.NotifyPropertyChanged("Enrollments");
            }
        }
        #endregion

        #region colAttendance
        private ObservableCollection<Attendance> _colAttendance
            = new ObservableCollection<Attendance>();
        public ObservableCollection<Attendance> colAttendance
        {
            get { return _colAttendance; }
            set
            {
                if (colAttendance == value)
                {
                    return;
                }
                _colAttendance = value;
                this.NotifyPropertyChanged("colAttendance");
            }
        }
        #endregion

        // Utility

        #region INotifyPropertyChanged
        public event PropertyChangedEventHandler PropertyChanged;

        private void NotifyPropertyChanged(String info)
        {
            if (PropertyChanged != null)
            {
                PropertyChanged(this, new PropertyChangedEventArgs(info));
            }
        }
        #endregion
    }
}