Deploying C# on Kubernetes: A Basic Guide for Developers

Deploying C# on Kubernetes: A Basic Guide

Kubernetes (K8s) has become the de facto standard for orchestrating containerized applications. If you develop in C# (.NET), sooner or later the question will arise: how to package your application and run it in the cloud or on your own cluster. In this guide, we will walk through the complete cycle — from creating a simple web API in ASP.NET Core to deploying it on Kubernetes.

This article is aimed at developers who are already familiar with the basics of C# and Docker, but are just starting to work with Kubernetes.

1. Preparing the .NET Application and Docker Image

Before deploying an application to Kubernetes, it needs to be packaged into a container. Let's create a minimal web API in C#.

1. Create a new project:

   dotnet new webapi -n MyK8sAppcd MyK8sApp

2. Ensure the application listens on port 80. In the Program.cs file (or appsettings.json), specify:

   builder.WebHost.UseUrls("http://0.0.0.0:80");

3. Create a Dockerfile in the project root:

   FROM mcr.microsoft.com/dotnet/aspnet:8.0 AS baseWORKDIR /appEXPOSE 80
   
   FROM mcr.microsoft.com/dotnet/sdk:8.0 AS buildWORKDIR /srcCOPY ["MyK8sApp.csproj", "."]RUN dotnet restore "./MyK8sApp.csproj"COPY . .RUN dotnet build "MyK8sApp.csproj" -c Release -o /app/build
   
   FROM build AS publishRUN dotnet publish "MyK8sApp.csproj" -c Release -o /app/publish
   
   FROM base AS finalWORKDIR /appCOPY --from=publish /app/publish .ENTRYPOINT ["dotnet", "MyK8sApp.dll"]

4. Build the image and push it to a registry (e.g., Docker Hub):

   docker build -t yourdockerhub/my-k8s-app:v1 .docker push yourdockerhub/my-k8s-app:v1

Important: Replace yourdockerhub with your actual username. For local testing, you can use minikube and skip publishing the image — just build it locally.

2. Creating Kubernetes Manifests

Kubernetes uses declarative YAML files to describe the desired state of the cluster. We will need two main objects: Deployment (pod management) and Service (network access).

2.1. Deployment

Create a file deployment.yaml:

apiVersion: apps/v1kind: Deploymentmetadata:  name: my-k8s-app-deployment  labels:    app: my-k8s-appspec:  replicas: 2  selector:    matchLabels:      app: my-k8s-app  template:    metadata:      labels:        app: my-k8s-app    spec:      containers:      - name: my-k8s-app        image: yourdockerhub/my-k8s-app:v1        ports:        - containerPort: 80        resources:          requests:            memory: "64Mi"            cpu: "250m"          limits:            memory: "128Mi"            cpu: "500m"        livenessProbe:          httpGet:            path: /health            port: 80          initialDelaySeconds: 5          periodSeconds: 10        readinessProbe:          httpGet:            path: /ready            port: 80          initialDelaySeconds: 3          periodSeconds: 5

In this manifest, we specify:

• replicas: 2 — two instances of the application for fault tolerance.
• resources — CPU and memory limits (important for stable cluster operation).
• livenessProbe and readinessProbe — health checks. Add /health and /ready endpoints to your controller.

2.2. Service

Create a file service.yaml:

apiVersion: v1kind: Servicemetadata:  name: my-k8s-app-servicespec:  selecto