I really like the new keyword async[^], though it is only available in Delphi Prism. The concept of futures[^] is just as nice. I hope both will make it into C# 4.
Here's a list of neat features[^] that are available in .NET 3.5, but tricky to use in C#.
I never would have thought I'd says that one day, but ... I'm beginning to like Prism...
Including that snippet and compiling with CSC 3.5 results in:
warning CS1685: The predefined type 'System.Runtime.CompilerServices.ExtensionAttribute' is defined in multiple assemblies in the global alias; using definition from 'c:\xt.cs'
xt.cs(26,42): warning CS0436: The type 'System.Runtime.CompilerServices.ExtensionAttribute'in'c:\xt.cs' conflicts with the imported type 'System.Runtime.CompilerServices.ExtensionAttribute'in'c:\Program Files\Reference<br />
Assemblies\Microsoft\Framework\v3.5\System.Core.dll'. Using the type defined in'c:\xt.cs'.
xt.cs(26,10): error CS1112: Do not use 'System.Runtime.CompilerServices.ExtensionAttribute'. Use the 'this' keyword instead.
It doesn't give warnings when you don't use the 3.5 libs
The reason to "avoid" it is that people generally don't want to download yet an other huge framework, it's usually hard enough to get people to agree to install 2.0
No. The question here presupposes that you are using 3.5 what about an option to say we haven't felt the need to use any of the features so the survey can reflect that it's not being used and help MS focus on what features people are using, i.e. features from 3.0 and 2.0.