How to manually detect arrow keys in gtk# c#

I am trying to make a game in Monodevelop using Gtk#-C# where the player moves a character around with arrow keys. However, arrow key presses are not being registered.

Is there a way to manually detect key presses, bypassing the default handler?

Multiple searches on both Google and Stack Overflow have not given an answer as to how to detect arrow keys using Gtk-C#.

This is the code I've been using to try and detect the arrow keys:

protected void Key_Press (object obj, KeyPressEventArgs args)
{
    //Let the rest of the program know what keys were pressed.
    if (pressedKeys.Contains (args.Event.Key))
        return;
    pressedKeys.Add (args.Event.Key, args.Event.Key);
}

And here is a basic program I made to attempt to figure out how to detect arrow keys:

public MainWindow (): base (Gtk.WindowType.Toplevel)
{
    Build ();

    this.KeyPressEvent += new KeyPressEventHandler (KeyPress);
}

protected void KeyPress (object sender, KeyPressEventArgs args)
{
    if (args.Event.Key == Gdk.Key.Up)
        return;

    label1.Text = args.Event.Key.ToString ();
}