Error in DockerFiles in AzureDevOps environment

Question

When performing the buils of a Net project. 7, in the DockerFile file I get an error in the following section:

RUN dotnet build "./Inventario/./Inventario.csproj" -c $BUILD_CONFIGURATION -o /app

Error: error CS5001: Program does not contain a static 'Main' method suitable for an entry point [/src/Inventario/Inventario.csproj]

Code DockerFile:

FROM mcr.microsoft.com/dotnet/aspnet:7.0 AS base
WORKDIR /app
EXPOSE 80
EXPOSE 443

FROM mcr.microsoft.com/dotnet/sdk:7.0 AS build
ARG BUILD_CONFIGURATION=Release
WORKDIR /src
COPY ["./Inventario.csproj", "Inventario/"]
RUN dotnet restore "./Inventario/./Inventario.csproj"
COPY . .
RUN dotnet build "./Inventario/./Inventario.csproj" -c $BUILD_CONFIGURATION -o /app

FROM build AS publish
ARG BUILD_CONFIGURATION=Release
RUN dotnet publish "./Inventario.csproj" -c $BUILD_CONFIGURATION -o /app/publish /p:UseAppHost=false 

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

What could be wrong with the DockerFile?

Thank you in advance, best regards

What could be wrong with the DockerFile?

Code YML:

- task: AzureCLI@2
  displayName: Docker Build
  inputs:
    azureSubscription: '$(azureSubscriptionEndpoint)'
    scriptType: 'bash'
    scriptLocation: 'inlineScript'
    inlineScript: |          
      find . -name "Dockerfile"            
      docker build -t service:$(tag) .
      docker save service:$(tag) -o service_$(tag).tar

Answer 1

Error: error CS5001: Program does not contain a static 'Main' method suitable for an entry point [/src/Inventario/Inventario.csproj]

I can reproduce the same issue when using the similar dockerfile.

The cause of the issue is that you are copying the .csproj file to the Inventario/(COPY ["./Inventario.csproj", "Inventario/"]), but all other project files are copied to the root folder(COPY . .).

In this case, the dotnet build command not able to find the Program.cs to find the main method.

To solve this issue, you need to copy the .csproj file and other project files to the same folder(root folder or Inventario/ folder).

For example: you can copy all files to Inventario/ folder

FROM mcr.microsoft.com/dotnet/aspnet:7.0 AS base
WORKDIR /app
EXPOSE 80
EXPOSE 443

FROM mcr.microsoft.com/dotnet/sdk:7.0 AS build
ARG BUILD_CONFIGURATION=Release
WORKDIR /src
COPY ["./Inventario.csproj", "Inventario/"]
RUN dotnet restore "./Inventario/./Inventario.csproj"
COPY . Inventario/
RUN dotnet build "./Inventario/./Inventario.csproj" -c $BUILD_CONFIGURATION -o /app

FROM build AS publish
ARG BUILD_CONFIGURATION=Release
RUN dotnet publish "./Inventario.csproj" -c $BUILD_CONFIGURATION -o /app/publish /p:UseAppHost=false 

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