using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Text;
using System.Windows.Forms;

namespace WindowsApplication1
{
    public partial class Form1 : Form
    {

        bool shaded = false;
        Size oldSize = Size.Empty;

        public Form1()
        {
            InitializeComponent();
        }

        protected override void WndProc(ref Message m)
        {
            if (m.Msg == NativeMethods.WM_SYSCOMMAND)
            {
                if (NativeMethods.Util.LOWORD(m.WParam) == NativeMethods.SC_MINIMIZE)
                {
                    if (shaded)
                    {
                        this.Size = oldSize;
                        this.shaded = false;
                    }
                    else
                    {
                        this.oldSize = this.Size;
                        this.Size = new Size(this.Width, 0);
                        this.shaded = true;
                    }
                    return;
                }
            }
            base.WndProc(ref m);
        }
    }

    static class NativeMethods
    {
        public const int WM_SYSCOMMAND = 0x112;
        public const int SC_MINIMIZE = 0xf020;

        public static class Util
        {
            public static int LOWORD(IntPtr p)
            {
                return LOWORD(unchecked((int)(long)p));
            }

            public static int LOWORD(int i)
            {
                return i & 0xFFFF;
            }
        }
    }
}