Code Snippet
private void btnDesabilitarTudo_Click(object sender, EventArgs e)
{
foreach(Control control in this.Controls)
DisableControls(control);
}
private void DisableControls(Control c)
{
if (c.GetType() != typeof(GroupBox))
c.Enabled = false;
if (c.Controls.Count == 0)
return;
foreach (Control control in c.Controls)
DisableControls(control);
}