.NET 2.0 = .NET 3.0 = .NET 3.5

Yesterday I had a discussion on an internal Microsoft Developers meeting about the status of .NET 3.5. We had presented that .NET 3.0 is an extension of .NET 2.0, and not a new version. My statement that the status of .NET 3.5 is the same, it is basically .NET 2.0 with extra features, was received sceptically.
Just to prove I'm right, here my observations.

Build a very simple .NET Console application, using two lines of code:

Console.WriteLine("Hello World");
Console.WriteLine("using version: {0}", System.Environment.Version.ToString());


With Visual Studio 2008, you can build this with all three version of the framework. And all three executables yields the same results: using version: 2.0.50727.1433.

ILDASM one of these assemblies gives the same assembly header:

// Metadata version: v2.0.50727
.assembly extern mscorlib
{
.publickeytoken = (B7 7A 5C 56 19 34 E0 89 )
.ver 2:0:0:0
}


Proving all three versions are based on the .NET core version 2.0 (and this is the same version you should configure in ASP.NET. There is no v3 there).
Just to be sure if you want to upgrade to 3.5 at your customer to mention that version 3.5 also is basically .NET 2.0, with some extra features added. I won't say that the libraries of .NET 2.0 are the same with 3.5, but runtime versions are equal.

Rick Strahl blogged about this a while ago.