Folks, creating new projects every day, with so many options for choosing the .NET version — what’s the difference? [caption id=“attachment_463” align=“aligncenter” width=“300”]
.NET versions installed on Windows[/caption]
Each new version of the .NET Framework keeps the features of earlier versions and adds new ones. The CLR is determined by its own version number. Some versions of the .NET Framework contain a new version of the CLR, while other versions use an earlier version of the CLR. For example, .NET Framework 4 contains CLR 4, while .NET Framework 3.5 contains CLR 2.0. (There is no CLR version 3.) Although .NET Framework 4.5 is an in-place update of .NET Framework 4, the underlying CLR version number becomes CLR 4.5. .NET Framework versions 2.0, 3.0, and 3.5 are built with the same version of the CLR (CLR 2.0). It’s impossible to run versions 2.0, 3.0, and 3.5 side by side on a computer. When you install .NET Framework 3.5 SP1, you automatically get the 2.0 and 3.0 layers. However, .NET Framework 4 abandons this layering approach. Starting with .NET Framework 4, in-process side-by-side hosting can be used to run multiple Common Language Runtime (CLR) versions in separate processes. Apps of versions 2.0, 3.0, and 3.5 can all run on version 3.5, but they won’t work on version 4 or higher. Supported versions.
| Client OS | Includes | Can also install |
|---|---|---|
| Windows 8 | .NET Framework 4.5 | .NET Framework 3.5 SP1 |
| Windows 7 | .NET Framework 3.5 SP1 | .NET Framework 4.5, .NET Framework 4 |
| Windows Vista SP2 | .NET Framework 3.0 SP2 | .NET Framework 4.5, .NET Framework 4, .NET Framework 3.5 SP1 |
| Windows XP Professional and Windows XP Home Edition | — | .NET Framework 4, .NET Framework 3.5 SP1, .NET Framework 2.0 SP2 |
| Server OS | Includes | Can also install |
| --- | --- | --- |
| Windows Server 2012 | .NET Framework 4.5 | .NET Framework 3.5 SP1 |
| Windows Server 2008 R2 | .NET Framework 2.0 SP2 (enabled by default), .NET Framework 3.5 SP1*, .NET Framework 3.0 SP2* | .NET Framework 4.5, .NET Framework 4 |
| Windows Server 2008 SP2 | .NET Framework 2.0 SP2 (enabled by default), .NET Framework 3.0 SP2* | .NET Framework 4.5, .NET Framework 4, .NET Framework 3.5 SP1 |
| Windows Server 2003 | .NET Framework 2.0 SP2 | .NET Framework 4, .NET Framework 3.5 SP1, .NET Framework 3.0 SP2 |
For more details, see MSDN: http://msdn.microsoft.com/library/bb822049.aspx