using System;
using System.Drawing;
using System.Windows.Forms;
public class PaintInvalidate : Form
{
private Button btn;
public PaintInvalidate()
{
Size = new Size(300,200);
btn = new Button();
btn.Parent = this;
btn.Location = new Point(25,25);
btn.Text = "Update";
btn.Click += new System.EventHandler(btn_Click);
}
static void Main()
{
Application.Run(new PaintInvalidate());
}
protected override void OnPaint(PaintEventArgs e)
{
base.OnPaint(e);
Graphics g = e.Graphics;
String str = "\nThe time is " + DateTime.Now.ToLongTimeString();
g.DrawString(str, Font, Brushes.Black, 50, 75);
}
private void btn_Click(object sender, EventArgs e)
{
Invalidate();
}
}