title: How to validate form data entry before navigation with WinForms in .NET using DataBindingNavigator?
body: <p>I'm just starting on .NET development with C#.  Although I'm getting comfortable with the language itself I need some help with the peculiarities of the framework.</p>
  
  <p>I'm building a windows forms application to replace a simple Access database.  I have the data source connected, dropped controls on the form, put the basic logic in place, no problems there.  Even figured out that I need to manually save the data back to the database using tableAdapterManager.UpdateAll(...) or similar.</p>
  
  <p>My current problem, which I've been unable to find a resolution to after much googling, is how to validate my data entry before allowing the user to leave the current record.</p>
  
  <p>Scenario:</p>
  
  <p>User clicks 'Add' to get a new record, fills in some of the data but doesn't fill in one of the required fields.  User then navigates to a different record without hitting the 'Save' button.  Application throws an exception and the record is lost.</p>
  
  <p>What event can I intercept, or what function do I need to override to do pre-navigation validation of my form's data and cancel navigation if the data is invalid in some way?</p>