Dockerized .NET App and Azure Web App Deployment with GitHub Actions

The classic "works on my machine" problem is real. Docker solves it by packaging your application with all its dependencies into a container. Combined with GitHub Actions for CI/CD, you get:

- Consistent environments: Dev, staging, and production run the exact same container - Automated testing: Run tests on every push before deploying - Zero-downtime deployments: Azure swaps containers seamlessly - Rollback capability: Previous container images are always available in the registry

A multi-stage Dockerfile keeps the final image small by separating the build environment from the runtime environment. The build stage uses the full .NET SDK, while the runtime stage uses the minimal ASP.NET runtime image.

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

FROM mcr.microsoft.com/dotnet/aspnet:8.0 AS runtime
WORKDIR /app
COPY --from=build /app/publish .
EXPOSE 8080
ENV ASPNETCORE_URLS=http://+:8080
ENTRYPOINT ["dotnet", "MyApp.dll"]

Azure Container Registry (ACR) stores your Docker images privately. Create one in the Azure portal or via CLI:

1. Create an ACR instance in your resource group 2. Enable Admin user for GitHub Actions authentication 3. Note the login server URL (yourname.azurecr.io) 4. Store credentials as GitHub repository secrets

ACR integrates natively with Azure Web App, so deployments pull images directly without external registries.

The CI/CD pipeline builds the Docker image, pushes it to ACR, and deploys to Azure Web App — all triggered on push to main.

# .github/workflows/deploy.yml
name: Build and Deploy to Azure

on:
  push:
    branches: [main]

jobs:
  build-and-deploy:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4

      - name: Login to ACR
        uses: azure/docker-login@v1
        with:
          login-server: ${{ secrets.ACR_LOGIN_SERVER }}
          username: ${{ secrets.ACR_USERNAME }}
          password: ${{ secrets.ACR_PASSWORD }}

      - name: Build and push image
        run: |
          docker build -t ${{ secrets.ACR_LOGIN_SERVER }}/myapp:${{ github.sha }} .
          docker push ${{ secrets.ACR_LOGIN_SERVER }}/myapp:${{ github.sha }}

      - name: Deploy to Azure Web App
        uses: azure/webapps-deploy@v2
        with:
          app-name: "my-web-app"
          images: "${{ secrets.ACR_LOGIN_SERVER }}/myapp:${{ github.sha }}"

Azure Web App for Containers needs a few settings:

- Container Settings: Point to your ACR image with the :latest or specific tag - Continuous Deployment: Enable webhook so Azure pulls new images automatically - Health Check: Configure a health check endpoint (/health) for zero-downtime deploys - App Settings: Set environment variables (connection strings, API keys) in Azure portal

Azure Web App automatically handles SSL, custom domains, scaling, and load balancing. Combined with Docker, you get enterprise-grade deployments with minimal configuration.