Understanding the Behavior of Windows Forms (C#) Development to Prevent Buttons from Being Pressed When Items Are Null

That's what I think.

• Prevents pressing as requested

  • Initially set Button.Enabled=false
  • Register event handlers for both ComboBox and TextBox TextChanged events
  • In those event handlers, it is determined whether the Text properties of both controls are valid data (IsNullOrEmpty/IsNullOrWhiteSpace), and Button.Enabled=true when both are valid data.If either data is invalid, use Button.Enabled=false.

• Pressable but not working

  <li> At the head of an event handler of a click event of Button, whether or not both Text properties of ComboBox and TextBox are valid data is determined, and when both are valid data, processing is performed when Button is depressed.If either data is invalid, no processing is performed, but an event handler is terminated by performing a warning/guide display or the like.

Make it impossible to press as requested

• Initially set Button.Enabled=false
• Register event handlers for both ComboBox and TextBox TextChanged events
• In those event handlers, it is determined whether the Text properties of both controls are valid data (IsNullOrEmpty/IsNullOrWhiteSpace), and Button.Enabled=true when both are valid data.If either data is invalid, use Button.Enabled=false.

Pressable but not working

<li> At the head of an event handler of a click event of Button, whether or not both Text properties of ComboBox and TextBox are valid data is determined, and when both are valid data, processing is performed when Button is depressed.If either data is invalid, no processing is performed, but an event handler is terminated by performing a warning/guide display or the like.