How To Disable Controls Of Master Page Used In Content Page While Processing Some Event

The following code works fine for disabling content page controls, but how do I disable master page controls?

public void DisableControls(Control control,bool isEnable)
{
if (control.HasControls())
{
foreach (Control c in control.Controls)
{
DisableControls(c, isEnable);
}
}
else
{
if (control is IPostBackDataHandler && !(control is IPostBackEventHandler))
{
if (control is WebControl)
{
((WebControl)control).Enabled = isEnable;
}
else if (control is HtmlControl)
{
((HtmlControl)control).Disabled = !isEnable;
}
}
}
}