TestApp Mono Runtime

NuGet.config

<configuration>
  <!-- Don't use any higher level config files.
       Our builds need to be isolated from user/machine state -->
  <fallbackPackageFolders>
    <clear />
  </fallbackPackageFolders>
  <packageSources>
    <clear />
    <!--
      'src/test/PrepareTestAssets/PrepareTestAssets.proj' generates a NuGet.config file using this
      one as a template. The following line is a marker to insert the test restore sources.
    -->
    <!-- TEST_RESTORE_SOURCES_INSERTION_LINE -->
    <add key="nuget.org" value="https://api.nuget.org/v3/index.json" />
    <add key="dotnet-tools" value="https://pkgs.dev.azure.com/dnceng/public/_packaging/dotnet-tools/nuget/v3/index.json" />
    <add key="dotnet-eng" value="https://pkgs.dev.azure.com/dnceng/public/_packaging/dotnet-eng/nuget/v3/index.json" />
    <add key="dotnet5" value="https://pkgs.dev.azure.com/dnceng/public/_packaging/dotnet5/nuget/v3/index.json" />
    <add key="dotnet5-transport" value="https://pkgs.dev.azure.com/dnceng/public/_packaging/dotnet5-transport/nuget/v3/index.json" />
    <add key="dotnet6" value="https://pkgs.dev.azure.com/dnceng/public/_packaging/dotnet6/nuget/v3/index.json" />
    <add key="dotnet6-transport" value="https://pkgs.dev.azure.com/dnceng/public/_packaging/dotnet6-transport/nuget/v3/index.json" />
  </packageSources>
  <disabledPackageSources>
    <clear />
  </disabledPackageSources>
</configuration>

TestApp.csproj

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

  <PropertyGroup>
    <OutputType>Exe</OutputType>
    <TargetFramework>net5.0</TargetFramework>
  </PropertyGroup>

  <ItemGroup>
    <KnownFrameworkReference Include="Microsoft.NETCore.App.Mono"
                              TargetFramework="netcoreapp5.0"
                              RuntimeFrameworkName="Microsoft.NETCore.App"
                              DefaultRuntimeFrameworkVersion="$(BundledNETCorePlatformsPackageVersion)"
                              LatestRuntimeFrameworkVersion="$(BundledNETCorePlatformsPackageVersion)"
                              TargetingPackName="Microsoft.NETCore.App.Ref"
                              TargetingPackVersion="$(BundledNETCorePlatformsPackageVersion)"
                              RuntimePackNamePatterns="Microsoft.NETCore.App.Runtime.Mono.**RID**"
                              RuntimePackRuntimeIdentifiers="linux-x64"
                              IsTrimmable="true"
                              />
    <FrameworkReference Remove="Microsoft.NETCore.App" />
    <FrameworkReference Include="Microsoft.NETCore.App.Mono" IsImplicitlyDefined="true" Pack="false" PrivateAssets="All" />
  </ItemGroup>

</Project>

You'll need to use dotnet run -r linux-x64 to make sure it uses the Mono runtime pack, a plain dotnet run will use coreclr.