UpdateSource on active field before deactivating window

Question

I have a program with a main window in which a user may alter data. The program also has a to-do-dialog, in which the user may see a list of stuff to do - and this dialog has it's own datacontext (connection to database) but needs to show let updated data.

I did not set UpdateSourceTrigger in all my fields in the main window to PropertyChanged (this wouldn't be wanted in all cases anyway because of functionality in the main window).

But I need the main window to do a updatesource on the "active" field in case the user activates the to-do-dialog so that the data may be saved to the database and re-read in the to-do-dialog.

If there were a "Deactivating" event on the window, I could use that to simply set focus to something else (forcing whatever currently focussed control to update it source). But no Deactivating event exists, only Deactivated which happens after the fact. And setting focus in the deactivated main window messes up up the activation of the to-do-dialog. Also, I cannot do this in the to-do-dialogs Actived event. A Activating event would have helped - but that does not exist.

Any good ideas how to force updatesource on my main window before the to-do-dialog gets activated (either by tabbing to it or by clicking it with the mouse)?

Answer 1

This kind of goes off of @AkselK's answer, but I find the keyboard focused control using the Keyboard.FocusedElement property and update the right bindings based on whether its a TextBox, Selector, or ToggleButton. I expected the Keyboard.FocusedElement to tell me the window I was swapping to is what has focus, but it actually does give me the control I was in inside the deactivating window.

void MyWindow_Deactivated(object sender, EventArgs e)
{
    if(Keyboard.FocusedElement is TextBox)
    {
        (Keyboard.FocusedElement as TextBox).GetBindingExpression(TextBox.TextProperty).UpdateSource();
    }
    else if(Keyboard.FocusedElement is Selector)
    {
        (Keyboard.FocusedElement as Selector).GetBindingExpression(Selector.SelectedItemProperty).UpdateSource();
        //todo: should this also update SelectedValueProperty?
    }
    else if(Keyboard.FocusedElement is ToggleButton)
    {
        (Keyboard.FocusedElement as ToggleButton).GetBindingExpression(ToggleButton.IsCheckedProperty).UpdateSource();
    }
}

I am unsure if the Selector portion should also update the binding for SelectedValue.