I have a XAML window showing your typical master detail relationship between an Air Waybill (AWB) and the charges on the AWB. The AWB charges are displayed/edited in a grid and there is a textbox on the form which shows the total of the charges in the grid. The textbox is defined like this:

                        <TextBox 
                            Name="txtAirWayBillTotal" 
                            Text="{Binding RelativeSource={RelativeSource FindAncestor, AncestorType={x:Type Window}}, Path=AirWayBillTotal}"
                            Grid.Column="3" 
                            Grid.Row="5" 
                            Height="23" 
                            HorizontalAlignment="Stretch" 
                            Margin="0" 
                            VerticalAlignment="Top" 
                            Width="Auto" 
                            Grid.ColumnSpan="2" 
                            HorizontalContentAlignment="Right" 
                            FontWeight="Bold" IsReadOnly="True" Focusable="False" />

The window has the AirWayBillTotal defined like this:

        private decimal airwaybillTotal;

        public decimal AirWayBillTotal
        {
            get
            {
                return this.airwaybillTotal;
            }

            set
            {
                if (value != this.airwaybillTotal)
                {
                    this.airwaybillTotal = value;
                    this.OnPropertyChanged("AirWayBillTotal");
                }
            }
        }

I have this code too:

        void AirWayBillDetail_StateChange(mmBaseBusinessObject bizObj, mmBusinessStateChangeEventArgs e)
        {
            if (e.State == mmBusinessState.Retrieved)
            {
                // Store the Air WayBill Detail in the DataGrid's data context
                this.grdAirWayBillDetails.DataContext = this.AirWayBillDetail.EntityList;

                // Hide the new item row place holder in the Air WayBill Detail DataGrid
                ((IEditableCollectionView)CollectionViewSource.GetDefaultView(grdAirWayBillDetails.ItemsSource)).NewItemPlaceholderPosition =
                    NewItemPlaceholderPosition.None;
            }
            //this.ShowAirWayBillTotal();
            if (this.AirWayBillDetail.EntityList != null)
            {
                this.AirWayBillTotal = this.AirWayBillDetail.EntityList.Sum(x => x.awd_amount);
                foreach (var c in this.AirWayBillDetail.EntityList)
                {
                    c.PropertyChanged += CollectionItemChanged;
                }
            }

        }

which as I understands it will call CollectionItemChanged whenever a value in the EntityList changes (but of course I may be misunderstanding).

My CollectionItemChanged code is:

        void CollectionItemChanged(object sender, PropertyChangedEventArgs e)
        {
            if (e.PropertyName == "awd_amount")
            {
                AirWayBillTotal = AirWayBillDetail.EntityList.Sum(x => x.awd_amount);
                OnPropertyChanged("AirWayBillTotal");
            }
        }

which checks if the value in the entitylist that was changed was awd_amount and if so, re-calculates the total.

My problem (finally) is that in certain instances the total does not get updated. This occurs when I add a new row to the charges grid, type in the new amount in the awd_amount column and then use Alt+S to call the Save button's click event. If I tab out of the column the total is updated. It is similar to when using a toolbar in VFP the current control is apparently not losing focus so the change is not registering.

Any ideas how to fix this?

(Thanks for reading this far!)