How do I disable updating a form in WinForms?

[DllImport("user32.dll")]
private static extern long LockWindowUpdate(long Handle);

try {
    // Lock Window...
    LockWindowUpdate( frm.Handle );
    // Perform your painting / updates...

} finally {
    // Release the lock...
    LockWindowUpdate( 0 );
}

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Text;
using System.Windows.Forms;
using Microsoft.Win32;
using System.Runtime.InteropServices;

namespace WindowsTest
{
  public partial class Form1 : Form
  {
    [DllImport("user32.dll")]
    public static extern int SendMessage(IntPtr hWnd, Int32 wMsg, bool wParam, Int32 lParam);
    private const int WM_SETREDRAW = 11;

    public Form1()
    {
      InitializeComponent();
    }

    private void button1_Click(object sender, EventArgs e)
    {
      SendMessage(this.Handle, WM_SETREDRAW, false, 0);

      // Do your thingies here

      SendMessage(this.Handle, WM_SETREDRAW, true, 0);

      this.Refresh();
    }
  }
}