WARNING: Could not resolve this reference. Could not locate the assembly "PackageName". Check to make sure the assembly exists on disk – Docker

need a little help resolving this issue I’m facing when building my ASP.NET project that references a local class library inside a docker container.

I’m using:

• ASP.NET 6.0
• Docker version 20.10.21, build baeda1f
• dotnet sdk 6.0

When I try to run
docker build .

I get the following error:

 => ERROR [build 7/7] RUN dotnet build "ProjectName.csproj" -c Debug -o /app/build                                                                                                                                                                       1.9s
------
 > [build 7/7] RUN dotnet build "ProjectName.csproj" -c Debug -o /app/build:
#15 0.434 MSBuild version 17.3.2+561848881 for .NET
#15 0.655   Determining projects to restore...
#15 0.885   All projects are up-to-date for restore.
#15 1.042 /usr/share/dotnet/sdk/6.0.404/Microsoft.Common.CurrentVersion.targets(2302,5): warning MSB3245: Could not resolve this reference. Could not locate the assembly "PackageName". Check to make sure the assembly exists on disk. If this reference is required
 by your code, you may get compilation errors. [/src/ProjectName/ProjectName.csproj]
#15 1.847 CSC : error CS5001: Program does not contain a static 'Main' method suitable for an entry point [/src/ProjectName/ProjectName.csproj]
#15 1.852
#15 1.852 Build FAILED.
#15 1.852
#15 1.852 /usr/share/dotnet/sdk/6.0.404/Microsoft.Common.CurrentVersion.targets(2302,5): warning MSB3245: Could not resolve this reference. Could not locate the assembly "PackageName". Check to make sure the assembly exists on disk. If this reference is required
 by your code, you may get compilation errors. [/src/ProjectName/ProjectName.csproj]
#15 1.852 CSC : error CS5001: Program does not contain a static 'Main' method suitable for an entry point [/src/ProjectName/ProjectName.csproj]
#15 1.852     1 Warning(s)
#15 1.852     1 Error(s)
#15 1.852
#15 1.852 Time Elapsed 00:00:01.38
------
executor failed running [/bin/sh -c dotnet build "ProjectName.csproj" -c Debug -o /app/build]: exit code: 1

The dockerfile I’m using

FROM mcr.microsoft.com/dotnet/aspnet:6.0 AS base
WORKDIR /app
EXPOSE 80
EXPOSE 443

FROM mcr.microsoft.com/dotnet/sdk:6.0 AS build
WORKDIR /src
COPY ["ProjectName.csproj", "ProjectName/"]
RUN dotnet restore "ProjectName/ProjectName.csproj"
COPY .. .
WORKDIR "/src/ProjectName"
RUN dotnet build "ProjectName.csproj" -c Publish -o /app/build

FROM build AS debug
RUN dotnet publish "ProjectName.csproj" -c Publish -o /app/publish

FROM base AS final
WORKDIR /app
COPY --from=publish /app/publish .
ENTRYPOINT ["dotnet", "ProjectName.dll"]

The .csproj file

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

    <PropertyGroup>
        <TargetFramework>net6.0</TargetFramework>
        <Nullable>enable</Nullable>
        <ImplicitUsings>enable</ImplicitUsings>
        <DockerDefaultTargetOS>Linux</DockerDefaultTargetOS>
    </PropertyGroup>

    <ItemGroup>
        ....
    </ItemGroup>

    <ItemGroup>
      <Reference Include="PackageName">
        <HintPath>....PackageNamePackageNamebinDebugnetstandard2.1PackageName.dll</HintPath>
      </Reference>
    </ItemGroup>

</Project>

Any thoughts on me getting the dockerfile to fetch the package .dll on build? or is it the wrong way to go about getting what I want?

I am open to hosting the package on nuget but for the time being this dockerfile is for dev purposes only.

Keep in mind that the package is at the right location locally, as building the project using:

dotnet build ProjectName.csproj

works fine

P.S. I replaced the package name with "PackageName" and the project name with "ProjectName".

I tried building the dockerfile for ASP.NET 6.0 and I expected it to pass, but I got an Error instead.