The current VS tooling generates a Dockerfile that looks like this:

FROM microsoft/aspnetcore-build:2.0 AS build WORKDIR /src COPY HelloWorld.sln ./ COPY HelloWorld/HelloWorld.csproj HelloWorld/ RUN dotnet restore -nowarn:msb3202,nu1503

This file does not copy the .dcproj into the container, even though the .sln file references the .dcproj. This was done to workaround a different error, error: MSB4236: The SDK 'Microsoft.Docker.Sdk' specified could not be found which happens when the .dcproj is present. However, this means the project setup is malformed. -nowarn:MSB3202 was added to suppress a legitimate warning about the malformed project setup. As we experienced between the 2.1.4 and 2.1.101 update, NuGet by default no longer coerces MSB3202 from an error to a warning, so -nowarn:MSB3202 does not prevent dotnet restore from failing.

Suggestion
Change the generated Dockerfile to include the .dcproj file when building inside the container, and let's find a way to solve the issue with MSB4236. Obviously, this needs more discussion as there are a few ways to do this, and we need to consider the impact of all them on the dotnet CLI, VS, Docker, etc.