Updating Custom Properties

   The TechTip on "Refreshing Dependent Parents" is excellent, but I thought I would try my hand on one of the tutorials.  I started with the Fundamental tutorial on "Populating a Winform".  First, I created a custom property for TotalCost:

public decimal TotalCost {
      get {
        decimal total = 0;
        foreach (OrderDetail detail in this.OrderDetails) {
          total += detail.UnitPrice * detail.Quantity;
        }
        return total;
      }
    }
Then, I added an OnColumnChanging Event Handler for OrderDetail:

    protected override void OnColumnChanged(DataColumnChangeEventArgs pArgs) {
      base.OnColumnChanged(pArgs);
      this.Order.ForcePropertyChanged(null);
    }

I thought that this would be all I needed, but I didn't see an immediate change in TotalCost.  As a last resort, I tried adding a ForcePropertyChanged for the Employee as well:

protected override void OnColumnChanged(DataColumnChangeEventArgs pArgs) {
    base.OnColumnChanged(pArgs);
    this.Order.ForcePropertyChanged(null);
    PrimaryKey pKey = new PrimaryKey(typeof(Employee), this.Order.EmployeeId);
    Employee aEmployee = (Employee)this.PersistenceManager.GetEntity(pKey);
    aEmployee.ForcePropertyChanged(null);
 }

I am not sure why the ForcePropertChanged on Employee is necessary, but I suspect it is because this tutorial uses chained bindings.