Asp – Are There Any Significant Changes in Localization Features Between VS2005/.NET 2.0, and VS2008/.NET 3.5

There's a difference between compiling and targeting.

Compiling the code with the (for example) C# 3.0 compiler will probably give you a boost on performance (very little one anyway) as some optimization for the generated IL code migh have been included. It also allows you to use some of the new features like automatic properties or lambda expressions.

Targeting for a given framework will ensure your assembly works for that framework (and posteriors) and will fail if you target for 2.0 and are using a 3.5 library. No performance improvements will be directly related to that unless your substituting a class from one framework with another "fastest" class. For example, targeting .NET 1.1 won't allow you to use generics and therefore you'll have to use the ArrayList which is considerably slower than List (due to boxing and unboxing).

You can use any new C# 3.0 feature that is handled by the compiler by emitting 2.0-compatible IL and doesn't reference any of the new 3.5 assemblies:

• Lambdas (used as Func<..>, not Expression<Func<..>> )
• Extension methods (by declaring an empty System.Runtime.CompilerServices.ExtensionAttribute)
• Automatic properties
• Object Initializers
• Collection Initializers
• LINQ to Objects (by implementing IEnumerable<T> extension methods, see LinqBridge)