I'm about to embark upon a rather mammoth project to write a broadcast control system from the ground up. My only real requirement is that is should be cross platform, the code should be able to run on a variety of platforms in particular windows, linux, OS X and Pocket PC with very little change (preferably none).

Until recently I would've used Qt to do this, simply because it seems to tick all the boxes and I know what I'm doing. The only thing I don't seem to be able to do is compile for Pocket PC with Qt, there is Qt Embedded but I don't know of many handhelds actually running Linux that are freely available in the UK.

I'm wondering wether it would be worth starting to learn C# and write it in .NET/Mono or stick with what I know with Qt? As an aside it looks like .NET would be the best way to make Pocket PC apps anyway.

Whilst doing cross platform back-end coding with C# is workable, the UI side of things is another matter. The PocketPC version of WinForms doesn't have all the functionality of WinForms on Windows. So you can't just take your Windows UI and chuck it onto the PocketPC (but then of course your typical Windows UI won't make sense on a PocketPC anyway).

On the OS X/Linux side of things, using the Mono .net stuff most of your Windows back-end C# will work without change (you can even compile with VS.NET and the run the code under Mono).

There is WinForms for OS X, but it probably isn't really ready for production work yet. When I ported a C# app from Windows to OS X I ran all my back-end code C# using Mono but recoded all the UI stuff in native Mac ObjectiveC code.

You also need to be careful if you are talking to databases and stuff like that, I don't know how far along the Mono database components are.

Your other option would be Java ... I don't know if you have a budget for this app, but IBM's J9 VM was really impressive with I tried it out on my iPAQ last year. You can buy it for $5.99 from Handango ( http://www.handango.com/PlatformProductD...ffiliateId=1218 ).