Comments by jabit (Top 3 by date)

NOT true, I solved it, finally! I serialized the data into XDocument's in memory and performed the swaps using XElement.Add() to set the missing cell values. There's a tiny bit of extra overhead converting the DataTable to XML and then back but overall my code is now nearly 30% faster!

I will change my question, I was hoping I could do some kind of join in code or just replace an entire datacolumn but it looks like you're right, looping is needed. However I want to do it without calling DataRow.set_Item for every item since that is where the time is taken. Microsoft doesn't support and recommends against accessing the SharePoint database directly, only through the API. Something I'm playing around with now is serializing the sharepoint data into XML in memory, performing all of the swaps against XmlNode's and then deserializing it back into a table, so far it looks promising!