Connect DataView or Drop-down List to SOAP Web Services on same server
Add a SOAP service as a data source
To be able to use a SOAP service on SharePoint 2010 as a data source in Designer, you will need to modify the web.config first. This article explains this:
Refer to this section for the instructions: "Configure the Web.config file on the server".
Follow the directions at the top of the page to connect to the web service. In my case I am investigating pulling in users in a SharePoint group as a data source for a webpart filter on a page. The customer wants to filter all the webparts of list views from a drop-down menu built from users in a group local to the site where the lists and page reside. I will need to allow for the default filter to be null or none, and then allow the filter to be refined by the user.