.Net FX 3.5 fully downward compatible ?
 

I just saw the new .Net FX 3.5 and realized I didn't even have 3.0 :O
Anyway, I was wondering about its downward compatibility, whether it's possible to install 3.5 only and still be able to run all .net apps ranging from 1.0 to 3.5...
I was once told it's better to install all frameworks (1 and 2 at that time) but I don't really like the idea of installing like 5 versions of that framework...

Does anyone have a clue about this ? I already googled a little but as always it just confuses you even more, some people say install all of them, MS says 3.0 includes 2.0, but I also read that there are compatibility issues with 1.1 apps running on 2.0... bah

BTW If anyone of you guys can find sn.exe I'd be glad if you could send it to me. It's supposed to be integrated into the framework but I couldn't find it, no luck via google either :-/

I don't know if the previous versions are needed... i installed all version (1.1; 2.0; 3.0; 3.5) and don't have problems with it.
(using WinVista Business 32bit)

I'm sure that, as with Java, there will always be people using code that is specific to a given version of the runtime environment. (*) So, nope, I don't think that, in general, you'll be able to run a software written for .NET version X in .NET version Y if X is not equal to Y. Most, well-written, software will work but some braindead ones won't. (Unless I'm very wrong and M$ was wiser in developing later versions of .NET than Sun was with Java... somehow, I doubt that. ;) But DirectX does seems to be downward compatible: when, in the early days of DirectX 3-5 or something, I had a problem with a game and manually uninstalled the latest DirectX and reinstalled the previous one, the game still didn't run and it turned out that rather the video card driver was not recent enough.)

(*) I think it was a workmate of mine who told me recently that, by a very wise move, IBM is now using Java-based installers for their software. However, their installers are so... khm... heterogeneous... that there are, actually, several different versions of the Java runtime environment embedded into the installer package so that all fragments of the Java code can run error free. Yes, that's right, they did not find and rewrite the specific code... Yippee! :D

"Fx 3.5 continues with the additive approach that we introduced with Fx 3.0 while still not introducing a new CLR. As a reminder, Fx 3.0 simply added to Fx 2.0 without changing or removing anything in the existing assemblies (it added WPF, WCF, WF and CardSpace). So, Fx 3.5 simply adds some assemblies to the existing set of DLLs that Fx 2.0/3.0 comprises of. This means that simply installing the framework should not affect your existing solutions. Note however that Fx 3.5 depends on Fx 2.0 SP1 and Fx 3.0 SP1, which will ship at the same time."

"The .NET Framework 3.5 is shipping later this year at the same time as Visual Studio 2008. The .NET Framework 3.5 is an additive release, meaning that it adds functionality in terms of classes in assemblies to the previous versions 3.0 and 2.0 of the .NET Framework. Since .NET Framework 3.5 doesn't replace (or install side by side) with .NET Framework 2.0 / 3.0 it is able to retain backward compatibility for applications built to .NET Framework 2.0 / 3.0. However there are two required service packs before you can install .NET Framework 3.5. They are .NET 2.0 SP1 and .NET 3.0 SP1, fortunately they are included in the distribution of .NET Framework 3.5. They will also be available for separate download from Microsoft and on Microsoft Update for existing customers who do not need .NET Framework 3.5 but still want the fixes."

guess its not backward compatible without those components...

apparently it emits IL code for .net 2.0 and backwards... lots of confusion about it, but then its newish, so expected

Thanks for the advice :)
Guess I'll just stick to my current approach, installing all of them ;)