Mounting report with ReportViewer in C #

I have two database tables that are the Purchase and Purchase Items. How can I make a report using ReportViewer .rdlc that meets the following pattern:

Dados da Compra    
   Dados itens da Compra         
   Dados itens da Compra 
Dados da Compra    
   Dados itens da Compra

Without using a table, using a list, because the various information would not be correct on a table.

I'm trying to send two DataTables to the Report, content the purchase data and the purchase items, until then I can. But how do I sync the data and generate that list by saying that those items from the purchase belong to that purchase.

The connection key of both tables are: Purchase- com_codigo; Items Purchased com_codigo;