When building a containerized .NET application offline, Docker fails even if all image layers are cached locally, because it still needs to fetch remote metadata to verify image manifests. The fix is to explicitly run `docker pull` for each base image referenced in the Dockerfile (e.g., `mcr.microsoft.com/dotnet/sdk:8.0` and `mcr.microsoft.com/dotnet/aspnet:8.0`) while online. This registers the images in the local image list without re-downloading layers, allowing offline builds to succeed.
