.NET Framework 2.0, 3.0 and 3.5

Visual Studio 2008 (code named Orcas) supports 3 versions of the .NET Framework. Thats a great feature because in the past you needed VS2002 for .NET 1.0, VS2003 for .NET 1.1 and VS2005 for .NET 2.0.

The fact that VS2008 supports the three most important versions of the framework is essential for a smooth upgrade path. I notice that there is still confusion about the differences between .NET 2.0 and 3.0, and 3.5 (beta). Time to outline some differences!

	.NET 1.1	.NET 2.0	.NET 3.0	.NET 3.5
CLR Version	CLR 1.1	CLR 2.0	CLR 2.0	CLR 3.0
C#-version	C# 1.0	C# 2.0	C# 2.0	C# 3.0
Pre-installed on OS	Windows Server 2003	Windows Server 2003 R2	Windows Vista	Windows Server 2008
Foundations	N/A	N/A	WPF WCF WF WCS	WPF WCF WF WCS
ADO	ADO.NET	ADO.NET 2.0	ADO.NET 2.0	ADO.NET vNext= LINQ
Special editions	.NET Compact Framework 1.0	.NET Compact Framework 2.0	.NET Compact Framework 2.0 .NET Micro Framework 2.0	.NET Compact Framework 3.5 Silverlight 1.1 .NET Micro Framework 2.0
New features			The 4 foundations	Faster garbage collection Smarter, faster NGen requiring smaller working set RAM 64 bit client improvements ThreadPool performance improvements Security check caching during NGen New class additions in BCL BigInteger HashSet TimeZone2 (info) Cryptography Integration with Event Tracing for Windows New Addin hosting model for extensibility Workflow enabled Services (codename 'Silver'). Build workflow-enabled services using WF and WCF. This allows a .NET Framework developer to build business logic for a service using WF and expose messaging from that service using WCF Build Ajax style web applications using WCF services Project templates for WCF services, WF business logic, workflow enabled services, and AJAX services in Visual Studio 2008 More WS-* Standards support RSS and ATOM syndication API Partial trust support for WCF hosting Improved rules engine WF and supports C# 3.0 features Visual Studio designer for WPF WPF has smoother animations, faster startup and better overall performance New data types available for data binding with LINQ Integration with Silverlight (source) More info about the new feature can be found here.

Version 3.0 is basically the same as 2.0, but contains the 4 new foundations:

• WPF, Windows Presentation Foudation;
• WCF, Windows Communication Foundation;
• WF, Windows Workflow Foundation;
• WCS, Windows CardSpace

Version 3.5 of the Framework is a bigger change. It contains a new compiler in order to handle the new programming language features and LINQ.

If you are about to install the .NET Framework, its better to install version 3.0. All 2.0-applications are compatible and version 3.5 is still in beta. By the way, you can run all version side-by-side (SxS, = on the same machine).

• .NET 3.0 is not a major change to the core .NET Framework as was 1.0/1.1 to 2.0
• If you currently have only .NET Framework 1.0 or 1.1 and you are looking to install 2.0 or 3.0
• If you currently have .NET Framework 2.0, installing .NET Framework 3.0 is not a major change as the version numbers would suggest
• If you currently run .NET 2.0 applications, they will not know or care that you have installed .NET 3.0

By the way, .NET versions can coexist in the same machines in the following directories:

v1.0.3705
v1.1.4322
v2.0.50727
v3.0
v3.5.20404