Containers for .NET Framework 4.6.2, 4.7, 4.7.1 actually contain 4.7.2 runtime

[paulmedynski]

I'm trying to find Windows containers with old .NET Framework versions installed to test with. I found this page that lists the different containers and their supported .NET Framework versions:

https://github.com/microsoft/dotnet-framework-docker/blob/main/README.runtime.md

I downloaded the containers for 4.6.2, 4.7, 4.7.1, and 4.7.2. When I checked the .NET Framework runtimes that were installed, the first 3 reported 4.7.03062, and the last one reported 4.7.03190. I believe both of those are internal versions of 4.7.2.

I verified this by creating a simple app that targets each of those framework versions. I mounted the executables in each container, and they all run in each container. For example, I ran 4 different executables in the 4.6.2 container and got these results:

Microsoft Windows [Version 10.0.14393]
(c) 2016 Microsoft Corporation. All rights reserved.

C:\>systeminfo | findstr /B /C:"OS Name" /C:"OS Version"
OS Name:                   Microsoft Windows Server 2016 Datacenter
OS Version:                10.0.14393 N/A Build 14393

C:\test>DotNetVersions.exe -b
4.0.0.0
4.7.03062

C:\test>bin\Debug\net462\FrameworkDescription.exe
Environment version: 4.0.30319.42000
System version: v4.0.30319
Framework name: .NETFramework,Version=v4.6.2
Framework display name:
OS version: Microsoft Windows NT 6.2.9200.0

C:\test>bin\Debug\net47\FrameworkDescription.exe
Environment version: 4.0.30319.42000
System version: v4.0.30319
Framework name: .NETFramework,Version=v4.7
Framework display name: .NET Framework 4.7
OS version: Microsoft Windows NT 6.2.9200.0

C:\test>bin\Debug\net471\FrameworkDescription.exe
Environment version: 4.0.30319.42000
System version: v4.0.30319
Framework name: .NETFramework,Version=v4.7.1
Framework display name: .NET Framework 4.7.1
OS version: Microsoft Windows NT 6.2.9200.0
OS description: Microsoft Windows 10.0.14393
OS architecture: X64
Process architecture: X64
Framework description: .NET Framework 4.7.4121.0

C:\test>bin\Debug\net472\FrameworkDescription.exe
Environment version: 4.0.30319.42000
System version: v4.0.30319
Framework name: .NETFramework,Version=v4.7.2
Framework display name: .NET Framework 4.7.2
OS version: Microsoft Windows NT 6.2.9200.0
OS description: Microsoft Windows 10.0.14393
OS architecture: X64
Process architecture: X64
Framework description: .NET Framework 4.7.4121.0

I wasn't expecting the 4.7+ executables to run, but they work fine presumably because the 4.6.2 container doesn't actually have the 4.6.2 runtime, but it has a 4.7.2 runtime instead.

Is this expected? I was hoping the 4.6.2 container would have the .NET Framework 4.6.2 runtime - not a newer one.

[lbussell]

According to .NET Framework versions and dependencies
, 4.6.2 should be installed by default on LTSC 2016, and later versions are installable.

Looking at the Dockerfile for 4.6.2-windowsservercore-ltsc2016, you can see that we only take the Windows base image and run Ngen on the .NET Framework assemblies:

dotnet-framework-docker/src/runtime/4.6.2/windowsservercore-ltsc2016/Dockerfile

Lines 1 to 10 in a6f890b

	# escape=`
	FROM mcr.microsoft.com/windows/servercore:ltsc2016-amd64
	ENV COMPLUS_NGenProtectedProcess_FeatureEnabled=0
	RUN `
	# ngen .NET Fx
	%windir%\Microsoft.NET\Framework64\v4.0.30319\ngen update `
	&& %windir%\Microsoft.NET\Framework\v4.0.30319\ngen update

I checked the .NET Framework versions in the base image mcr.microsoft.com/windows/servercore:ltsc2016-amd64 using both the DotNetVersions tool and the registry and got the same results as you.

I think this means the Windows Container team is installing 4.7.2 on the base image. Since 4.7.2 is an in-place upgrade to 4.* versions, there shouldn't be any compatibility issues. I did validate that a simple .NET Fx app with a net462 TargetFramework runs fine on the 4.6.2 runtime image.

You could file an issue on the microsoft/Windows-Containers repo asking about the pre-installed .NET Framework versions on the base image.

[paulmedynski]

Thank you for looking into this @lbussell - I will followup with the Windows Container folks (microsoft/Windows-Containers#562).

I checked an older version of your 4.6.2 image (4.6.2-20190312-windowsservercore-ltsc2016) and it does indeed come with .NET Framework 4.6.2:

C:\test>DotNetVersions.exe -b
4.0.0.0
4.6.01586

PS C:\test> .\GetDotNetVersion.ps1

.NET Framework Product Version   Release
-------------- ------- -------   -------
Client         4.6.2   4.6.01586  394802
Full           4.6.2   4.6.01586  394802
Client                 4.0.0.0

I can use that for my current testing.

[paulmedynski]

A couple of follow-up questions:

I see from the page you linked that 4.6.2 comes pre-installed on Windows Server 2016, and that 4.7.2 comes pre-installed on Windows Server 2019, and that you're using those base container images for your corresponding 4.6.2 and 4.7.2 images.

I also see that you're using Server 2016 as the base image for your 4.7 and 4.7.1 images, however those images also appear to have 4.7.2 installed (due to the base image coming with 4.7.2 I assume).

The Dockerfiles for your 4.7 and 4.7.1 images are attempting to install those .NET Framework versions. Are those install commands silently failing currently since the LTSC 2016 base image comes with a newer Framework (4.7.2)?

If I go back in time to some of the 4.7 and 4.7.1 images created in 2019 (like I did for 4.6.2), will I find that those have the intended .NET Framework versions?

Thanks!

[lbussell]

I'm in touch with the .NET Framework servicing team internally, so I'll get back to you on this soon.