1.0 obsolete
1.1 VS 2003
  * win 2003 has built in


2.0 (sp1) VS 2005/8/(?)10
3.0 WPF, WCF, WF, VS 2005/8/(?)10
3.5 (sp1) Linq, C#3.5, Entity fw..., sp1: System.Web.Abstraction, Sys.Web.Routing. VS 2008/(?)10
  * win 2008 has built in
  * the same runtime
  * upgrade is convinient (not risky , backward compat)


4.0 VS 2010
  * new machine.config, mscorlib, runtime
  * C#4.0, ASP.NET 4.0
  * upgrade might be risky, requeres changes in web.config.

mono
  * integration with VS
  * MonoDev
  * The Mono API today is somewhere in between .NET 2.0 and .NET 3.5,
  * cross platform

 

 

we recommend:

VS 2008/.NET 3.5
  * C# 3.5
  * all-in-one technologies.
  * upgrade from .NET 2.0 does not require any code change

MONO for cross platform only.

VS 2010/.NET 4.0 - in the future.