How to include dependencies in .NET Core app docker image?

Question

I'm trying to build a .NET Core app docker image. But I can't figure out how I'm supposed to get the project's NuGet dependencies into the image.

For simplicity reasons I've create a .NET Core console application:

using System;
using Newtonsoft.Json;

namespace ConsoleCoreTestApp
{
    public class Program
    {
        public static void Main(string[] args)
        {
            Console.WriteLine($"Hello World: {JsonConvert.False}");
        }
    }
}

It just has one NuGet dependency on Newtonsoft.Json. When I run the app from Visual Studio, everything works fine.

However, when I create a Docker image from the project and try to execute the app from there, it can't find the dependency:

# dotnet ConsoleCoreTestApp.dll
Error: assembly specified in the dependencies manifest was not found -- package: 'Newtonsoft.Json', version: '9.0.1', path: 'lib/netstandard1.0/Newtonsoft.Json.dll'

This is to be expected because Newtonsoft.Json.dll is not being copied by Visual Studio to the output folder.

Here's the Dockerfile I'm using:

FROM microsoft/dotnet:1.0.0-core
COPY bin/Debug /app

Is there a recommended way of dealing with this problem?

I don't want to run dotnet restore inside of the container (as I don't want to re-download all dependencies everytime the container runs).

I guess I could add a RUN dotnet restore entry to the Dockerfile but then I couldn't use microsoft/dotnet:<version>-core as base image anymore.

And I couldn't find a way to make Visual Studio copy all dependencies into the output folder (like it does with regular .NET Framework projects).

Answer 1

After some more reading I finally figured it out.

Instead of dotnet build you run:

dotnet publish

This will place all files (including dependencies) in a publish folder. And this folder then can be used directly with a microsoft/dotnet:<version>-core image.