Winforms button sample

using System;
using System.Windows.Forms;
using System.Drawing;
using System.Drawing.Drawing2D;

public class MyClass
{
    Button btn;
    bool isValid = true;

    public static void Main()
    {
        new MyClass();
    }

    public MyClass()
    {
        var form = new Form();
        btn = new Button();
        btn.Size = new Size(50, 50);
        btn.Paint += Button_Paint;
        btn.Click += Button_Click;
        form.Controls.Add(btn);
        Application.Run(form);
    }

    private void Button_Paint(object sender, PaintEventArgs e)
    {
        Graphics g = e.Graphics;
        if (isValid) {
            g.DrawString("This is a diagonal line drawn on the control",
                new Font("Arial", 10), System.Drawing.Brushes.Blue, new Point(30, 30));
            g.DrawLine(System.Drawing.Pens.Red, btn.Left, btn.Top,
                btn.Right, btn.Bottom);
        }
        else {
            g.FillRectangle(
                new LinearGradientBrush(PointF.Empty, new PointF(0, btn.Height), Color.White, Color.Red),
                new RectangleF(PointF.Empty, btn.Size));
        }
    }

    private void Button_Click(object sender, EventArgs e)
    {
        isValid = false;
        btn.Invalidate();
    }
}