We have a C# DLL (let’s call it myapp.exe) built with .NET 2.0 Framework (VS2005) and we found out that our application won’t work on machines where only .NET 4.0 or above is installed. To let our application work on .NET 4.0, I added the following some lines to myapp.exe.config by following this article Installing .NET Framework V4.0 and Running .NET 2.0/3.0/3.5/3.5Sp1 Applications
<startup>
<supportedRuntime version="v4.0.30319"/>
</startup>
And it is working.
Then I saw that this article also mentioned the following (especially second paragraph):
Now, I knew that you can’t just take a 3.5 Service Pack 1 application
and run it
on the V4.0 CLR. It needs a V2.0 CLR or reconfiguring with a
tag in order to bend the application to run on the V4.0 CLR and that bending might
be something that you don’t want to do.What I hadn’t realised though was that installing .NET 4.0 wouldn’t install the
bits that you need for a 2.0/3.0/3.5/3.5Sp1 application. It would only install
the V4.0 CLR and the V4.0 assemblies and not additionally install the equivalent
of .NET Framework V3.5 Sp1. So, you’d need to install (e.g.) .NET Framework V3.5 Sp1
yourself along with .NET 4.0
From my testing it would mean that I could run my 2.0 C# application on .NET 4.0 with .NET 4.0 framework (4.0 assembly/libraries) which is contradicting to what the articles said.
Or am I missing something here? It could be helpful if someone could clarify on this. Microsoft doesn’t really make this clear at all.
You can run your application on .NET 4 using the .NET 4 assemblies. There is always the possibility that there may be a slight change in runtime behavior, however, as you won’t be using the same runtime and framework which you used for development. I suspect the article is trying to suggest that you won’t get the exact same behavior by just installing 4.0, though, as you’ve seen, it should work.
Doing this is likely fine, though I would recommend doing thorough testing of your application if this is going to be a standard deployment option.