>Hi Viv, I'm using NPOI which is good for my purposes I've gone down the churning row by row route which is ok it works and there is no particular performance requirement for this tool - but as ever if you know a better way ? Back to my other question , I've built a collection (generic List ) of my custom class for the serialisation utility but I can't seem to query it using Linq i.e. intellisense not showing any Where or First - as I need to filter out some of the duplicates it would be useful to use Linq - any ideas ?

Only the obvious one : do you have a 'using' for System.Linq - if not then the Linq extension methods won't be available...

Which remind me that, if you're using NPOI, then you could look at this library : https://github.com/paulyoder/LinqToExcel.
I haven't used it but I believe it works with NPOI. Documentation is a bit sparse though,
There's a demo here : https://code.google.com/p/linqtoexcel/ (with a link to some examples on the 'Read Me' page