In this guide, we'll walk through the steps to containerize a .NET API using Docker and set up a CI/CD pipeline with GitLab. This setup enables automatic building, testing, and deployment of your application, ensuring a smoother development lifecycle.
✅ Prerequisites
Before getting started, make sure you have the following:
- A .NET API project (.NET 8 or compatible)
- A GitLab account with a repository
- Docker installed on your local machine
🐳 Dockerizing the .NET API
- Create a Dockerfile in the root of your project directory. This file defines how to build your Docker image.
# Base image for running the app
FROM mcr.microsoft.com/dotnet/aspnet:8.0 AS base
WORKDIR /app
EXPOSE 80
EXPOSE 443
# Build image
FROM mcr.microsoft.com/dotnet/sdk:8.0 AS build
WORKDIR /src
COPY ["blog.backend.api/blog.backend.api.csproj", "blog.backend.api/"]
RUN dotnet restore "blog.backend.api/blog.backend.api.csproj"
COPY . .
WORKDIR "/src/blog.backend.api"
RUN dotnet build "blog.backend.api.csproj" -c Release -o /app/build
# Publish image
FROM build AS publish
RUN dotnet publish "blog.backend.api.csproj" -c Release -o /app/publish /p:UseAppHost=false
# Final image
FROM base AS final
WORKDIR /app
COPY --from=publish /app/publish .
ENTRYPOINT ["dotnet", "blog.backend.api.dll"]
⚙️ Setting Up the GitLab CI/CD Pipeline
- Create a .gitlab-ci.yml file at the root of your repository:
image: docker:latest
services:
- docker:dind
stages:
- build
- test
- deploy
variables:
DOCKER_IMAGE: registry.gitlab.com/yash-project/blogApplicationAPI
DOCKER_TAG: latest
build:
stage: build
script:
- docker build -f Dockerfile -t $DOCKER_IMAGE:$DOCKER_TAG .
- echo "$CI_REGISTRY_PASSWORD" | docker login -u "$CI_REGISTRY_USER" --password-stdin $CI_REGISTRY
- docker push $DOCKER_IMAGE:$DOCKER_TAG
test:
stage: test
image: mcr.microsoft.com/dotnet/sdk:8.0
script:
- dotnet test
deploy:
stage: deploy
script:
- echo "Deploying using Docker Compose..."
- docker-compose up -d
only:
- main
This pipeline includes three stages:
- Build: Builds and pushes the Docker image to GitLab's container registry.
- Test: Runs your unit/integration tests.
- Deploy: Spins up the container using Docker Compose.
📦 Docker Compose Deployment
Create a docker-compose.yml file:
version: "3.9"
services:
blog-backend-api:
image: registry.gitlab.com/yash-project/blogApplicationAPI:latest
ports:
- "80:80"
- This simple setup pulls the latest image and runs your API on port 80.
🎯 Conclusion
By combining Docker with GitLab CI/CD, you now have a robust and automated workflow for building, testing, and deploying your .NET API. This approach streamlines development and ensures consistency across environments.
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