WPF datagrid: DataGridCheckBoxColumn events

Question

In my WPF project I have build the following datagrid with checkbox column:

XAML

<DataGrid AutoGenerateColumns="False"
          TargetUpdated="IsIntermediatePointFixedByBracketDataGrid_TargetUpdated">
        <DataGrid.Columns>               
            <DataGridCheckBoxColumn Binding=
                "{Binding isFixedByBracket, NotifyOnTargetUpdated=True }" />
        </DataGrid.Columns>
</DataGrid>

C#

private void IsIntermediatePointFixedByBracketDataGrid_TargetUpdated(object sender,
    DataTransferEventArgs e)
{
    DataGrid dg = (DataGrid)sender;
    if (dg.SelectedIndex != -1 
        && ((IsFixedByBracketElement)dg.SelectedItem).isFixedByBracket
        != this.currentIntermediatePosition.isFixedByBracket[dg.SelectedIndex])
    {
        this.currentIntermediatePosition.isFixedByBracket[dg.SelectedIndex] = 
                    ((IsFixedByBracketElement)dg.SelectedItem).isFixedByBracket;
    }
}

When I check/uncheck a checkbox, the TargetUpdated event is thrown, but the value changes only if I select and deselect the cell that contains the checkbox. Why does this happen? How can I change this behavior?

Solution

The Reason for this is because the default behavior of binding inside CellTemplates are UpdateSourceTrigger=LostFocus.

Change to :

<DataGridCheckBoxColumn Binding="{Binding isFixedByBracket, NotifyOnTargetUpdated=True ,
                        UpdateSourceTrigger=PropertyChanged }" />