Docker Mounted DotNet Watch Run

readme.md

This gist demonstrates a problem experienced when using dotnet run within a docker container. The command works fine outside of the container, but when running the container we run into a problem wherein NuGet references cannot be resolved outside of the container, so vscode or visual studio will report problems if you start the compose project.

To test this out, copy the files to your computer in a new directory. Open the directory with either editor (vscode or vs). Run the following comand and observe the errors in your editor that appear at the using PSValueWildcard; statement in Program.cs.

docker build . -t docker-dotnet-watch && docker run -v .:/src docker-dotnet-watch

DockerCompose.csproj

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

  <PropertyGroup>
    <OutputType>Exe</OutputType>
    <TargetFramework>net7.0</TargetFramework>
    <Nullable>enable</Nullable>
  </PropertyGroup>

  <ItemGroup>
    <PackageReference Include="PSValueWildcard" Version="1.0.0-alpha1" />
  </ItemGroup>

</Project>

Dockerfile

FROM mcr.microsoft.com/dotnet/sdk:7.0
WORKDIR /src
CMD dotnet build

Program.cs

using System;
using System.Threading;
// this reference fails to be resolved after running the compose project (or container alone)
using PSValueWildcard;

public sealed class Program
{
    public static void Main()
    {
        Console.WriteLine("Hello, World!");
    }
}

https://natemcmaster.com/blog/2018/05/12/dotnet-watch-2.1/#support-for-running-in-docker

The solution is to add the following Directory.Build.props file to the project or solution directory.

<Project>

  <PropertyGroup>
    <DefaultItemExcludes>$(DefaultItemExcludes);$(MSBuildProjectDirectory)/obj/**/*</DefaultItemExcludes>
    <DefaultItemExcludes>$(DefaultItemExcludes);$(MSBuildProjectDirectory)/bin/**/*</DefaultItemExcludes>
  </PropertyGroup>

  <PropertyGroup Condition="'$(DOTNET_RUNNING_IN_CONTAINER)' == 'true'">
    <BaseIntermediateOutputPath>$(MSBuildProjectDirectory)/obj/container/</BaseIntermediateOutputPath>
    <BaseOutputPath>$(MSBuildProjectDirectory)/bin/container/</BaseOutputPath>
  </PropertyGroup>

  <PropertyGroup Condition="'$(DOTNET_RUNNING_IN_CONTAINER)' != 'true'">
    <BaseIntermediateOutputPath>$(MSBuildProjectDirectory)/obj/local/</BaseIntermediateOutputPath>
    <BaseOutputPath>$(MSBuildProjectDirectory)/bin/local/</BaseOutputPath>
  </PropertyGroup>

</Project>