Assembling report with Reportviewer in C#

Question

I have two tables in the database that are Purchase and Purchase Items. How is it possible to make a report using Reportviewer . rdlc that stays with 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 in a table.

I am trying to send two Datatable to the Report, content the purchase data and the purchase items, until then I get it. But how do I synchronize the data and generate this list, saying that those purchase items belong to that purchase.

The link key of both tables are: Buyout- with code Itenscompra- code;