.NET › Docker & Containerization

How would you optimize a Docker image build for a solution with multiple .NET projects sharing common dependencies, to maximize layer cache reuse?

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Answer

Restructure the Dockerfile to copy all .csproj/.sln files first (preserving the directory structure needed for project references) and run a single `dotnet restore` against the solution before copying any actual source code, so the expensive restore step (resolving potentially dozens of shared NuGet dependencies across all projects) is cached and reused as long as none of the project files change, even if application source code changes frequently.

# Copy project files first, preserving directory structure for references
COPY *.sln .
COPY src/MyApi/*.csproj src/MyApi/
COPY src/MyLib/*.csproj src/MyLib/
RUN dotnet restore

# THEN copy all source code (invalidates cache more often, but restore stays cached)
COPY . .
RUN dotnet publish -c Release -o /app/publish

Real-world example A monorepo with 15 interdependent projects restructures its Dockerfile using this pattern, cutting typical CI build time significantly since the shared dependency restore step (previously re-run on every build) is now cached across builds that only touch application code.

Common follow-ups: How does this pattern scale as the number of projects grows very large?;What's the trade-off of this more complex Dockerfile versus simplicity?

.NET CLI SDK & Project Structure (csproj);CI/CD Publishing & Deployment