Visual Studio 2015 Web Test with Data from Oracle Database
If you can connect to the DB but you don't see the needed tables it should be a permission issue.
Do you use same credentials from "VS->Server Explorer" to connect to the DB?
If this is not the case, do you have more than one Oracle clients installed in your system? If yes, then most probably, the DataSource control uses the wrong client and the "Server Explorer" the correct one.
Are you using synonyms as proxies for your tables (e.g. for permission reasons)? synonyms will not show up when querying the list of tables that the user can access. They need be queried separately. When only the available tables are queried but not the vendor specific aliases this might lead to an empty list.
You need to install ODAC for Visual Studio 2015 to view the database tables. Here is the link for it.http://www.oracle.com/technetwork/topics/dotnet/downloads/odacmsidownload-2745497.html