title: VFP - FoxPro - Textbox: how to distinguish between empty input and 0 input
body: <p>I'm maintaining a legacy VFP application.</p>
  
  <p>There is a textbox for numeric input.
  In the validate event I want to check if the user entered a number or left the textbox empty.</p>
  
  <p>How can I detect if the user left the field with no characters/numbers in it?</p>
  
  <p>Unfortunately I cannot distinguish if the user entered a 0 or completely deleted the characters in the textbox. This.Value is 0 in both cases and VARTYPE(This.Value) is "N" and EMPTY(This.Value) is .T.</p>
  
  <p>Background: later really entered numbers should go as the number to the database whereas a deleted input field should be stored as .NULL. (yes the corresponding table column accepts Null-values)</p>