We are holding all our data in MS SQL Server 2008 as Easting/Northing against the British National Grid. Unfortunately ESRI needs the data plotted to Web Mercator.
So I've ended up using Proj.Net for the British National Grid (27700) to WGS84 (4326) conversion
Then for the WGS84 (4326) to Web Mercator (102100) conversion I used the code in this article.
This gives me usable data within ESRI, however plotted points aren't quite in the right place. It seem that I'm suffering from the shift because the datum hasn't been changed. This post suggests that Proj.Net can correct the datum shift by specifying the
TOWGS84 parameter, but I don't understand what this means.
I'd prefer a C# library or code that got from British National Grid to Web Mercator in one quick, simple conversion. However if I need to jump through hoops, I'll do that, but could do with some extra guidance