dataset xml related tables. c#

this sounds like such a common thing to do but i cant find the specific
answer on the net.

i have 2 tables, say orders and customers.

i want to use the dataset to return the orders/customers in xml in the
following format:

<Order>
<OrderId>1</OrderId>
<Cutstomer>
<CustomerId>12<CustomerId>
<CustomerName>Bob Murray<CustomerName>
</Customer>
<OrderDetail>some goods</OrderDetail>
</Order>

how can i do this?

i have using 2 separate selectcommands on each table, then creating a
relationship between the 2 tables, but for some reason the dataset.getxml
method is returning ALL customers, even if they have no orders.

thanks in advance!