Multi-Targeting .NET Framework & .NET Core

[RehanSaeed]

Steps to reproduce the issue

I'd like to be able to build my project targeting .NET Framework (Mono) and .NET Core.

Expected behavior

A docker image exists with both the .NET Framework (Mono) and .NET Core.

Actual behavior

No such image exists.

Additional information

I was not certain where to raise this issue, so I've also raised it here.

[akoeplinger]

The easiest solution would be to take the Mono image and just install .NET Core in your Dockerfile, or the other way around :)

[RehanSaeed]

That's exactly what I'm now looking into.

Multi-targeting is a fairly common scenario, particularly for library authors. and I don't want to have to maintain a docker image. I was hoping that a more expansive image could be created but I'm not sure who would maintain it.

I suppose this is a more general problem with docker images and not being able to somehow merge them when you want dependencies from two base images. I'm sure docker are on it.

[akoeplinger]

You don't need to maintain a persistent Docker image yourself, you'd just install .NET Core as normal in the Dockerfile and create a temporary image before invoking your build script.

[RehanSaeed]

I'm trying to use Circle CI, to build NuGet packages. So I don't actually have a Dockerfile. Plus I'd rather not maintain all this with each version update.

[akoeplinger]

Yeah, understood. I think it'd need to be driven by the .NET Core team since they'd need to make it work on Windows with .NET Framework as well.

[dnperfors]

I just tried it the other way around, I took the .NET Core docker image and installed mono in there like this:

FROM microsoft/dotnet:2.0-sdk AS build-env

ENV MONO_VERSION 5.10.0.160

RUN apt-key adv --keyserver hkp://keyserver.ubuntu.com:80 --recv-keys 3FA7E0328081BFF6A14DA29AA6A19B38D3D831EF

RUN echo "deb http://download.mono-project.com/repo/debian stable-jessie/snapshots/$MONO_VERSION main" > /etc/apt/sources.list.d/mono-official-stable.list \
  && apt-get update \
  && apt-get install -y mono-runtime binutils curl mono-devel ca-certificates-mono fsharp mono-vbnc nuget referenceassemblies-pcl \
  && rm -rf /var/lib/apt/lists/* /tmp/*

ENV FrameworkPathOverride=/usr/lib/mono/4.5/

WORKDIR /app
COPY . .

RUN dotnet build -c Release -o out

FROM mono
WORKDIR /app
COPY --from=build-env /app/MyTestApp/out ./
ENTRYPOINT ["mono", "MyTestApp.exe"]

My test application has a 'normal' project file and a .NET Core style project file targeting the .NET Framework (something I am experimenting with) and this works great.
I think it would be helpful to have this as an official container :)

[akoeplinger]

The .NET team is working on getting the .NET Framework reference assemblies into a NuGet package so you can build using the .NET Core tooling as well which I guess solves this too: dotnet/designs#33

[markteovel14]

My application is a .NET Framework it is possible to run a docker image with mono?
Thanks!

[iceagebuck]

Is there any progress on this request? I have similar requirement.