Azure DevOps Pipeline failure - Program does not contain a static 'Main' method suitable for an entry point

Question

I have been tasked with deploying an email service to an Azure tenant using Windows Containers. In my Pipeline (Azure DevOps), I am receiving the following error when in the build step:

CSC : error CS5001: Program does not contain a static 'Main' method suitable for an entry point.

I believe my docker file is not correct. It was autogenerated from VS2022 and it doesn't resemble the docker files I've used in the past. Also, the Repo is TFVC.

Any assistance would be greatly appreciated.

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 ["FACTS_SendMail/FACTS_SendMail.csproj", "FACTS_SendMail/"]
COPY ["/FACTS_SendMail.csproj", "FACTS_SendMail/"]
RUN dotnet restore "FACTS_SendMail/FACTS_SendMail.csproj"
COPY . .
WORKDIR "/src/FACTS_SendMail"
RUN dotnet build "FACTS_SendMail.csproj" -c Release -o /app/build

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

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

Answer 1

Move the WORKDIR "/src/FACTS_SendMail" line right above the "COPY . ." line. This solved the issue for me. Apparently setting the working directory before helps in copying the restored packages from dotnet restore to the right place. Not sure I understand it fully but fixed it for me.