gistfile1.txt

using System;
using System.Windows.Forms;

public class Sample1:Form
{
	private Label lb;
	private TextBox tb;

	public static void Main(){
		Application.Run (new Sample1 ());
	}

	public Sample1(){
		this.Text ="Sample";
		this.Width = 200;
		this.Height = 200;

		lb = new Label ();
		lb.Text = "Welcome";
		lb.Dock = DockStyle.Top;

		tb = new TextBox ();
		tb.Dock = DockStyle.Bottom;

		lb.Parent = this;
		tb.Parent = this;

		tb.KeyDown += new KeyEventHandler (tb_KeyDown);

	}

	public void tb_KeyDown(Object sender, KeyEventArgs e){
		//senderにはObjectとして色々情報が入っている。
		//その中からTextBoxの情報をCastで取り出しているよ
		TextBox tmp = (TextBox)sender;
		if (e.KeyCode == Keys.Enter) {
			lb.Text = tmp.Text+" is selected";
		}
	}
}