I have a textbox that is bound to a property that requires a value, ie:

 [Required(ErrorMessage = "required value")]
 public string SomeText
 {
     //get set...
 }

And in my XAML, I have the following setup for my textbox: 

 UpdateSourceTrigger=PropertyChanged, ValidatesOnDataErrors=true, ValidatesOnExceptions=true

As expected, the red border appears when there is no value in the textbox, however when I select a different tab and then go back to the page with the invalid results, the red border no longer appears. It only reappears if I enter a valid result and then erase it.

How can I debug this? How can I find out what event causes the red border to appear?

wpf validation textbox
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