What does this have to do with 'Showcases' ? PLease post in the right forum next time.
about your question:
you can add the datasourcecontrols to the toolbox when you have a webform open in vs.net. This is a vs.net limitation, so we can't do a thing about that.
the dll should be available in the .net references, if not you can browse to it. What vs.net version are you using?