dave

I am binding a 3-state checkbox to an XElement:

<CheckBox Content="Summary" IsChecked="{Binding
Path=Element[StatusSummary].Value, Mode=TwoWay,
UpdateSourceTrigger=PropertyChanged}" IsThreeState="True" IsEnabled="False"
Margin="0,79,0,0"/>

it properly reports True and False when it is checked or unchecked. but it
retains the previous value when in the intermediate state. it would seem to
not be firing the propertychanged event to update the xelement when
transitioning to the indeterminate state. Is there a way to bind to get back
the null for indeterminate?