Obtains the Type for the System.Web.UI.WebControls.Xml control's specified child control.
The System.Web.UI.ControlBuilder.GetChildControlType(string, IDictionary) method is overridden to always return null.
The XmlBuilder.GetChildControlType(string, IDictionary) method of the System.Web.UI.WebControls.XmlBuilder class overrides the System.Web.UI.ControlBuilder.GetChildControlType(string, IDictionary) method of the System.Web.UI.ControlBuilder class. This implementation of the XmlBuilder.GetChildControlType(string, IDictionary) method always returns null.