https://learn.microsoft.com/en-us/dotnet/api/system.windows.forms.keypresseventargs.handled?view=netframework-4.8.1&viewFallbackFrom=windowsdesktop-7.0
KeyPressEventArgs.Handled Property (System.Windows.Forms) | Microsoft Learn
Gets or sets a value indicating whether the KeyPress event was handled.
property systemwindows formshandledmicrosoftlearn