public class SalesRow : INotifyPropertyChanged
{
 #region Private Fields
 private event PropertyChangedEventHandler propertyChanged;
 private string label;
 private int[] values;
 #endregion

 #region Constructors
 public SalesRow()
 {
  this.label = "";
  this.values = new int[4];
 }

 public SalesRow(string label, int[] values)
 {
  if (values == null)
  {
   throw new ArgumentNullException();
  }

  if (values.Length != 4)
  {
   throw new ArgumentException();
  }

  this.label = label;
  this.values = values;
 }
 #endregion

 #region Public Events
 public virtual event PropertyChangedEventHandler PropertyChanged
 {
  add { this.propertyChanged += value; }
  remove { this.propertyChanged -= value; }
 }
 #endregion

 #region Private Methods
 protected virtual void OnPropertyChanged(string propertyName)
 {
  PropertyChangedEventHandler handler = this.propertyChanged;
  if (handler != null)
  {
   handler(this, new PropertyChangedEventArgs(propertyName));
  }
 }
 #endregion

 #region Public Properties
 public virtual string Label
 {
  get { return this.label; }
  set
  {
   if (this.label != value)
   {
    this.label = value;
    this.OnPropertyChanged("Label");
   }
  }
 }

 public virtual int Q1
 {
  get { return this.values[0]; }
  set
  {
   if (this.values[0] != value)
   {
    this.values[0] = value;
    this.OnPropertyChanged("Q1");
    this.OnPropertyChanged("Year");
   }
  }
 }

 public virtual int Q2
 {
  get { return this.values[1]; }
  set
  {
   if (this.values[1] != value)
   {
    this.values[1] = value;
    this.OnPropertyChanged("Q2");
    this.OnPropertyChanged("Year");
   }
  }
 }

 public virtual int Q3
 {
  get { return this.values[2]; }
  set
  {
   if (this.values[2] != value)
   {
    this.values[2] = value;
    this.OnPropertyChanged("Q3");
    this.OnPropertyChanged("Year");
   }
  }
 }

 public virtual int Q4
 {
  get { return this.values[3]; }
  set
  {
   if (this.values[3] != value)
   {
    this.values[3] = value;
    this.OnPropertyChanged("Q4");
    this.OnPropertyChanged("Year");
   }
  }
 }

 public virtual int Year
 {
  get
  {
   int sum = 0;
   foreach (int value in values)
   {
    sum += value;
   }
   return sum;
  }
 }
 #endregion
}