Docker and Containerization for ASP.NET Core

Introduction

Docker packages ShopNest API + dependencies into portable images — same container runs on your laptop, Azure, or client data center. Multi-stage builds keep images small.

After this article you will

• Write multi-stage Dockerfile
• Use Docker Compose with SQL + Redis
• Configure env vars and volumes
• Add HEALTHCHECK and .dockerignore
• Push to Azure Container Registry

Prerequisites

• Article 59 — Deploying to IIS
• ShopNest solution builds and tests pass locally

Concept deep-dive

# Dockerfile — ShopNest.Api
FROM mcr.microsoft.com/dotnet/sdk:8.0 AS build
WORKDIR /src
COPY . .
RUN dotnet restore ShopNest.Api/ShopNest.Api.csproj
RUN dotnet publish ShopNest.Api/ShopNest.Api.csproj -c Release -o /app

FROM mcr.microsoft.com/dotnet/aspnet:8.0 AS final
WORKDIR /app
COPY --from=build /app .
EXPOSE 8080
HEALTHCHECK CMD curl -f http://localhost:8080/health/ready || exit 1
ENTRYPOINT ["dotnet", "ShopNest.Api.dll"]

# docker-compose.yml
services:
  api:
    build: .
    ports: ["8080:8080"]
    environment:
      ConnectionStrings__Default: "Server=sql;Database=ShopNest;User=sa;Password=..."
    depends_on: [sql, redis]
  sql:
    image: mcr.microsoft.com/mssql/server:2022-latest
  redis:
    image: redis:7-alpine

Hands-on — ShopNest Microservices Application

1. docker build -t shopnest-api .
2. docker-compose up — API + SQL + Redis.
3. .dockerignore excludes bin/obj.
4. VS 2022 Container Tools attach debugger.

Common errors & best practices

• SDK image in production — use aspnet runtime only in final stage.
• Linux container on Windows without switching — mode mismatch.
• Secrets in Dockerfile ENV — use secrets/compose env files.

Interview questions

Q: Container vs VM?
A: Containers share OS kernel — lighter, faster start than full VMs.

Q: Multi-stage build?
A: Build in SDK image; copy published output to slim runtime image.

Summary

• Multi-stage Dockerfile for small production images
• Compose runs full ShopNest stack locally
• Health checks integrate with orchestrators
• ACR for private Azure images

Previous: Deploying to IIS
Next: Azure App Service

FAQ