GetService(XmlEditorService) is coming null

hi,

I am trying to write a custom editor by following http://code.msdn.microsoft.com/xmlwpfdesigner. in the sample in the EditorPane(WindowPane).INitalize method

it is getting instance of XmlEdtitorService as

XmlEditorService es = GetService(typeof(XmlEditorService)) as XmlEditorService;

But in my code, im getting this as null. Even the msdn says that the service can be obtained like this. http://msdn.microsoft.com/en-us/library/microsoft.visualstudio.xmleditor.xmleditorservice.aspx

But i am not able to get this service instance.

Do i have to do something extra so that IServcieProvider.GetService will return me a service of type XmlEditorService.?