Avoid duplicates in the destination schema - schema

Question

I have a little problem. I want to map every detail line to one OrderInfo. The destination schema can not have any duplicate OrderInfo. All the detail lines should be in the destination orderInfo, but the SuppliersOrderNo and BuyersOrderNo should not be twice.
Any ideas how to do this, is it possible to use XSL or inline script?
<inv:OrderInfo>
<inv:SuppliersOrderNo>123456</inv:SuppliersOrderNo>
<inv:BuyersOrderNo>6789</inv:BuyersOrderNo>
<inv:DetailLines>
<inv:DetailLine>
<inv:InvoiceDetailLineNo>1</inv:InvoiceDetailLineNo>
<inv:Item>
<inv:SuppliersArticleNo>article2</inv:SuppliersArticleNo>
<inv:SuppliersDescription>BestArticle</inv:SuppliersDescription>
</inv:Item>
</inv:DetailLine>
<inv:DetailLine>
<inv:InvoiceDetailLineNo>2</inv:InvoiceDetailLineNo>
<inv:Item>
<inv:SuppliersArticleNo>article3</inv:SuppliersArticleNo>
<inv:SuppliersDescription>AlmostBestArticle</inv:SuppliersDescription>
</inv:Item>
</inv:DetailLine>
</inv:DetailLines>
</inv:OrderInfo>
<inv:OrderInfo>
<inv:SuppliersOrderNo>123456</inv:SuppliersOrderNo>
<inv:BuyersOrderNo>6789</inv:BuyersOrderNo>
<inv:DetailLines>
<inv:DetailLine>
<inv:InvoiceDetailLineNo>1</inv:InvoiceDetailLineNo>
<inv:Item>
<inv:SuppliersArticleNo>article1337</inv:SuppliersArticleNo>
<inv:SuppliersDescription>WOW</inv:SuppliersDescription>
</inv:Item>
</inv:DetailLine>
</inv:DetailLines>
</inv:OrderInfo>

Answer 1

If you want to do this purely in XSLT, you'll have to use Muenchian gruoping. I wrote a blog that links to some other blogs on how to do this in BizTalk a little while back: https://blog.tallan.com/2014/12/09/muenchian-grouping-in-biztalk-while-keeping-mapper-functionality/
To summarize the blog: if you pursue this, you'll need a map that's completely custom XSLT somewhere, but you could put it into a custom pipeline component if you still want to be able to use "regular" maps functionality without any other caveats (in my blog I describe a method of doing that in a pipeline component so that a "regular" BizTalk map can still be used on the preprocessed output). There are lots of resources on Muenchian grouping out there (including on StackOverflow), so I'm not rehashing all of that in this answer.
You could also try to serialize the message in a C# component and use some LINQ methods to group/sort/order/etc, or if you're inserting the content into SQL at some point you could do it in SQL (which would be able to handle this kind of task more naturally).