How do I disable updating a form in Windows Forms?

I don't find SuspendLayout() and ResumeLayout() do what you are asking for. LockWindowsUpdate() mentioned by moobaa does the trick. However, LockWindowUpdate only works for one window at a time.

You can also try this:

using System;
using System.Windows.Forms;
using Microsoft.Win32;
using System.Runtime.InteropServices;

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();
    }
}

You can use the old Win32 LockWindowUpdate function:

[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);
}

I think this.SuspendLayout() & ResumeLayout() should do it