TIL: Set Docker Environment Variables in Visual Studio for easier debugging

Today I learned how to set Docker Environment Variables directly in Visual Studio to ease my debugging experience.

I really googled a lot to find an easy solution for this simple problem - and tried many different ways to pass variables directly into my attached docker container - but it took way too long to discover this StackOverflow post. Hopefully my post helps someone else, too!

I even read the excellent docs from asp.net core - but there is no mention how to pass docker environment variables directly to the container so that you can debug them. In my side-project I have an asp.net core web app that needs one or more configuration parameters that can be set with the -e switch in the docker run command:

docker run -e "PAT=123" image

But I want to have a Visual Studio debugger attached so that I can debug into my code as seen in the following screenshot:

Following the accepted answer in the StackOverflow post, I created a file called “settings.env” and filled it with key/value pairs. Lines starting with # are comments:

#Personal Access Token to write back the plan output to Azure DevOps
PAT=[Personal Access Token]
PROJECT=[Azure DevOps Project URL]
VARIABLE=[Filename of the variable file including extension]
WORKSPACE=[Name of the default workspace]

Then I edited my project (.csproj) file and added

<DockerfileRunEnvironmentFiles>settings.env</DockerfileRunEnvironmentFiles>

to a PropertyGroup-tag so it looks like the following:

<Project Sdk="Microsoft.NET.Sdk.Web">

  <PropertyGroup>
    <TargetFramework>netcoreapp2.1</TargetFramework>
    <DockerTargetOS>Linux</DockerTargetOS>
    <DockerDefaultTargetOS>Linux</DockerDefaultTargetOS>
    <DockerfileRunEnvironmentFiles>settings.env</DockerfileRunEnvironmentFiles>
  </PropertyGroup>

</Project>

The I started the debugger with F5 and finally I can easily debug my solution even with docker environment variables:

Hope it helps,
Max