Modifying Design link URLs in Connect Edition using C# or VBA

I have a requirement from a customer to write a (once only throw-a-way) tool to run through a number of DGN files and update the base address in all of the link URLs. The links are a mixture of Engineering links (older V8i generated ones) and design links (newer connect edition generated ones). They are in the process of moving the linked file to a new SharePoint site (on-prem to O365)

Modifying V8i Engineering links look to be straight forward using VBA as they are implemented using TAGS. However the Connect Edition design links are a different story as it looks like they are stored using XAttributes from what I can tell.

I am seeking some advice and possibly sample code that I can adapt/include in a .NET (C#) command line program/tool to handle the newer form of links.