How to use datatable filter


I’m trying to learn how to use datasets and bought the book "Build your own ASP.NET3.5 WEB SITE 3rd edition and in the book it talks breifly about Filtering data pages 542 and 543 with a line of code:
dataTable.DefaultView.RowFilter = “Department LIKE ‘a%’”;

there is no reference to dataTable is this a typo?

My end goal is to pass a filter parameter from a ddlist to filter the current datasets default view.