.Net 4.0 targeting on windows 8.x

Question

I'm a bit confused about targeting .net 4.0 app to run on windows 8.x. In my understanding, windows 8.0 comes with 4.5 and windows 8.1 comes with 4.5.1. So my question, if I build a WinForms or WPF client app targeting c#/.net 4.0 (in Visual Studio Project settings) and of course only using .net 4.0 features (ie, no features from .net 4.5.x), then will this app run fine on windows 8.x without having install .net 4.0 framework (that is, only relying on what comes installed with OS)? Basically, I'm trying to avoid forcing end user to install .net 4.0 framework on their machine before running the app.

Looking at DLLs properties of various Microsoft DLLs (eg, System) they show same runtime version when targeting either .net 4.0 or .net 4.5.x --> v4.0.30319. So my understanding here is that 4.0 and 4.5.x are targeting same clr runtime version So, my .net 4.0 app should run fine???

From ref here ( http://msdn.microsoft.com/en-us/library/bb822049%28v=vs.110%29.aspx ), it says .net 4.0 can't even be installed on win8.x.

In my tests, targeting .net 4.0 and running on clean install of win8.1 seems to work fine (without having to install anything else) but looking for advice on gotchas.

Thanks.

Answer 1

Note that the .NET framework is intrinsically backwards compatible - .NET 4.5 will execute .NET 4.0 code just fine. This can be seen even within a solution in that a .NET 4.5/4.5.1 project can reference an older .NET project without incident. This includes .NET 4.0, as well as earlier versions.

In addition to the backwards compatibility, .NET 4.5 does run on the CLR 4.0 - 4.5 is simply a library and compiler expansion.

Possible gotchas

• This emphasis on backwards compatibility is why we almost never see functions disappear from the .NET Framework, just get marked [Obsolete] . it's a good idea to check if any functions you use have become Obsolete, though this is rare and such functions usually continue to work as expected.
• Windows 8 does NOT like Drive mapping, and will demand that you use UNC paths if you application touches any networks drives.
• Windows 8 can be far more aggressive with requiring Admin privileges to run, up to and including needing to explicitly start VS as admin when trying to compile a program which outputs to C:\\Program Files\\...

Final note: ALWAYS test your application on the targeted platform before releasing to users.

Answer 2

Per this question :

.NET Framework 4.5 was released on 15 August 2012., a set of new or improved features were added into this version. The .NET Framework 4.5 is only supported on Windows Vista or later. The .NET Framework 4.5 uses Common Language Runtime 4.0, with some additional runtime features.

I would say then that by virtue of having .NET 4.5 installed you will also always have .NET 4.0 installed. I don't think this should be an issue then!

Answer 3

From the link you posted:

Each new version of the .NET Framework retains features from the previous versions and adds new features.

Also from that link:

The .NET Framework 4.5 is an in-place update that replaces the .NET Framework 4 on your computer, and similiarly, the .NET Framework 4.5.1 4.5.2, and 4.6 Preview are in-place updates to the .NET Framework 4.5, which means that they use the same runtime version, but the assembly versions are updated and include new types and members.

So, if a system has 4.5, it will be able to run apps targeted for 4.0 as well. The fact that some versions cannot be installed most likely only means that they are already included from the start.