c# - Boolean Statement True For Length of Time

I have the following code:

private Boolean _penny = false;

public void InputTextbox_KeyDown(object sender, KeyEventArgs e)

{
   if (!_penny)
   {
      if (e.KeyCode == Keys.Enter & InputTextbox.Text.Contains("penny"))
      {
         _penny = true;
         OutputTextbox.Text = "yes sir";
         InputTextbox.Text = "";
      }
   }

}

This clears the InputTextbox so that it is ready for further input, and the commands that follow only run if the Boolean for _penny = true (ie: that the program has been ordered to listen for further commands).

At the moment, each text command ends with "_penny == false" so that the program essentially stops listening for anything.

My question is, can this Boolean value stay "true" for a length of time? ie: User says "penny", and they can ask multiple input questions for a number of minutes without having to say "penny" again.

Answer

While you could use a timer, that seems like overkill to me. All you need to do is track an expiry date/time:

private bool CurrentlyValidated
{
  get
  {
    return DateTime.Now < _expiryTime && _validated ;
  }
  set
  {
    _validated  = value ;

    _expiryTime = DateTime.Now.AddMinutes(5) ;
  }
}
private bool     _validated  ;
private DateTime _expiryTime ;