sample1.cs

using System;
using System.Windows.Forms;

class Sample1 : Form {
    private Label lb, lb2;
    private Button bt;

    public static void Main() {
        Application.Run( new Sample1() );
    }
    public Sample1() {
        this.Text = "サンプル";
        this.Width = 200; this.Height = 200;

        lb = new Label();
        lb.Text = "矢印キーを入力";
        lb.Width = 150;

        lb2 = new Label();
        lb2.Text = "方向";
        lb2.Top = lb.Bottom;

        lb.Parent = this;
        lb2.Parent = this;

        // イベントハンドラを登録する
        this.KeyDown += new KeyEventHandler( fm_KeyDown );
    }

    // イベントハンドラを定義する
    public void fm_KeyDown( Object sender, KeyEventArgs e ) {
        String str;
        if       ( e.KeyCode == Keys.Up ) {
            str = "上";
        } else if( e.KeyCode == Keys.Down ) {
            str = "下";
        } else if( e.KeyCode == Keys.Left ) {
            str = "左";
        } else if( e.KeyCode == Keys.Right ) {
            str = "右";
        } else {
            str = "他のキー";
        }
        lb2.Text = str + "ですね。";
    }
}