title: Data validation on ShowDialog window in WPF
body: <p>I have a window that I display as ShowDialog
  in the window I have some textboxes binding to object that implement INotifyPropertyChannges and IDataErrorInfo.
  I want that the OK button will enabled just if all thextboxes validted
  and I want that just if the user click on OK buton the next move will occur.</p>
  
  <p>I can bind the button to ICommand and check the textboxes valitation in CanExcute() but then what can I do in the Excute? the object dont know about the window.
  I can also check the textboxes valitation and then raise event that all valid and enable the OK button but then there will be dupliacte code because I checked already in the IDataErrorInfo implmention.</p>
  
  <p>So what is the right way?</p>
  
  <p>Thanks in advance</p>