By default, when you tab out of a TextBox whose Text property is data bound, the value is pushed to the data source. Data validation occurs as part of this process.
When you create a BindingGroup and the Binding becomes part of this BindingGroup, the value is no longer pushed to the data source when the TextBox loses focus. This is what I want. However, the data validation no longer occurs. This is
not what I want.
How do I validate a binding that is part of a BindingGroup on LostFocus without updating the source? I want my users to have immediate feedback of data entry errors but I want to retain control over when data is pushed to the data source.
It would be great if this could be implemented as a style in a Theme.xaml file or any other solution that would not require hooking up to each and every LostFocus event handler in my application.
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