Changing datasource in Crystal .NET

There is serveral ways to do that, depending on which version of Crystal, edition (standalone or not) and database (OLEDB, ODBC, XML, File based one...).
This is knowledge base article for VB.NET and Crystal Reports 9:

http://support.businessobjects.com/library/kbase/articles/c2010371.asp

Important part is looping through - tables that you have to loop through are not really table objects, but also views or stored procedures, depending of what exactly do you have as source.
Moreover, each and every subreport should be updated too with new datasource information.