OnKeyPress Fun Example

type
  TfrmMain = class(TForm)
    edtName: TEdit;
    procedure edtNameKeyPress(Sender: TObject; var Key: Char);
  private
    { Private declarations }
  public
    { Public declarations }
  end;

var
  frmMain: TfrmMain;

implementation

{$R *.dfm}

procedure TfrmMain.edtNameKeyPress(Sender: TObject; var Key: Char);
begin
  // Fun code to demonstrate Chr() and Ord() functions
  // This line adds 1 to the ASCII character code that is typed
  //Key := Chr(Ord(Key) + 1);

  // Code to prevent ASCII characters other than numbers from being typed
  // Every character other than 0 to 9 is replaced with a null character
  if (Ord(Key) < 48) or (Ord(Key) > 57) then Key := #0;
end;

end.