You can do this, but the way is indirect. The key to your path is the ADO.NET DataRelation Class. You can find pre-written help on Microsoft’s support site:
326080 HOW TO: Implement a DataSet JOIN helper class in Visual C# .NET
325688 HOWTO: Implement a DataSet JOIN helper class in Visual Basic .NET
These are a part of a series and Microsoft seems to have lost the index page, so you can find the others by entering the following into a Google search box:
“dataset helper class” site:support.microsoft.com
Or, enter ‘Dataset “helper class”‘ on the Microsoft KnowledgeBase search page:
Go ahead and use the DataSet JOIN helper class but make sure you at least look over the code to find out how joins can be emulated by using the DataRelation.