How do I disable all controls in ASP.NET page

foreach (Control c in this.Page.Controls)
{
    if (c is DropDownList)
        ((DropDownList)(c)).Enabled = false;
}

protected void DisableControls(Control parent) {
    foreach(Control c in parent.Controls) {
        if (c is DropDownList) {
            ((DropDownList)(c)).Enabled = false;
        }

        DisableControls(c);
    }
}

protected void Event_Name(...) {
    DisableControls(Page); // use whatever top-most control has all the dropdowns or just the page control
}

For Each c As Control In parentControl.Controls
        If TypeOf (c) Is CheckBox Then
            CType(c, CheckBox).Enabled = enable
        ElseIf TypeOf (c) Is RadioButtonList Then
            CType(c, RadioButtonList).Enabled = enable
        End If
        SetControls(c)
    Next

End Sub

protected void Page_Load(object sender, EventArgs e)
{
  DisableChilds(this.Page);
}

private void DisableChilds(Control ctrl)
{
   foreach (Control c in ctrl.Controls)
   {
      DisableChilds(c);
      if (c is DropDownList)
      {
           ((DropDownList)(c)).Enabled = false;
      }
    }
}

<body>
    <form id="form1" runat="server">
      ...
    </form>
</body>

protected void Page_Load(object sender, EventArgs e)
{
	form1.Disabled = true;
}