ERROR IN FOREACH LOOP

public void ClearAllControls(Control ctrl)
    {
        foreach (Control eachctrl in ctrl)
        {
            if (eachctrl is TextBox)
            {
                ((TextBox)(eachctrl)).Text = "";
            }
            if (eachctrl is DropDownList)
            {
                ((DropDownList)(eachctrl)).SelectedIndex = 0;
            }
  &n ...