.NET 3.5 with Service Pack 1, .NET 3.5 SP1, .NET 3.5.1, .NET 3.51. Are they all the same thing?

Question

I'm researching version info about .NET Framework 3.5 and I have 3 questions.

1) My web searches turned up several names: .NET 3.5 with Service Pack 1, .NET 3.5 SP1, .NET 3.5.1, .NET 3.51. Are they all the same thing?

2) My Registry shows I have .NET 3.5 SP1 installed (version 3.5.30729.4926). If I use Visual Studio 2010 to develop an app on this computer, would the app run in .NET 3.5 without any problems? Visual Studio C# doesn't seem to have a Target Framework selection specifically for .NET 3.5 SP1.

3) What's generally considered as the most widely installed/used version of .NET now? .NET Framework 3.5 SP1 or 4.0?

Thanks in advance for sharing your knowledge.

Answer 1

There's no such thing as .NET 3.5.1 or .NET 3.51. However, ".NET 3.5 with Service Pack 1" is the same as ".NET 3.5 SP1".

If you install Visual Studio 2010, you should target .NET 3.5 if you want it to run on that - if you're not careful, your programs will require .NET 4. It's easy to do this though - you can either specify the framework when you create the project, or change it later in the project properties.

As for what's most widely installed - I suspect .NET 3.5 is more widespread than .NET 4 at the moment, as .NET 4 has only been released for 4 months. Over time I'd expect its adoption to increase, of course. Having said that, I doubt you'll find many machines with .NET 4 but without .NET 3.5SP1. (I suspect it's possible, but I haven't tried.) One important question is what your target audience is - if most users will also be .NET developers, for example, then you can probably expect them to be more sympathetic to installing .NET 4.