We had an ASP.NET site that was built on .NET 2.0. It had sharepoint integration and everything was working fine until the site got migrated to .NET 4.0. I know that sharepoint is built on 3.5 framework and hence it is failing now. Are there any workarounds or any latest developments to make sharepoint work on ASP.NET 4.0 site?
Me and my string.IsNullOrWhitespace / named parameter loving self wishes this was possible, but it most assuredly is not yet possible. The closest you can get is if you were to utilize SOA and (obviously) your services could be written in .NET 4.0 (or any language for that matter), but your web parts, workflows, feature receivers, modules, etc are stuck in legacy 3.5.
Additionally, the "next" edition of SharePoint (SharePoint Online) which is part of Office 365 is just SharePoint 2010 with cloud compatibility... and still no .NET 4.0.