Containerize a .NET application

Table of contents

Prerequisites

You have installed the latest version of Docker Desktop.
You have a git client. The examples in this section use a command-line based git client, but you can use any client.

Overview

This section walks you through containerizing and running a .NET application.

Get the sample applications

In this guide, you will use a pre-built .NET application. The application is similar to the application built in the Docker Blog article, Building a Multi-Container .NET App Using Docker Desktop.

Open a terminal, change directory to a directory that you want to work in, and run the following command to clone the repository.

$ git clone https://github.com/docker/docker-dotnet-sample

Initialize Docker assets

Now that you have an application, you can create the necessary Docker assets to containerize it. You can choose between using the official .NET images or Docker Hardened Images (DHI).

Docker Hardened Images (DHIs) are minimal, secure, and production-ready container base and application images maintained by Docker. DHI images are recommended for better security—they are designed to reduce vulnerabilities and simplify compliance.

Docker Hardened Images (DHIs) for .NET are available in the Docker Hardened Images catalog. Docker Hardened Images are freely available to everyone with no subscription required. You can pull and use them like any other Docker image after signing in to the DHI registry. For more information, see the DHI quickstart guide.

Sign in to the DHI registry:
$ docker login dhi.io
Pull the .NET SDK DHI (check the catalog for available versions):
$ docker pull dhi.io/dotnet:10-sdk
Pull the ASP.NET Core runtime DHI (check the catalog for available versions):
$ docker pull dhi.io/aspnetcore:10

You can use docker init to generate Docker assets, then modify the Dockerfile to use DHI images:

$ docker init
Welcome to the Docker Init CLI!

This utility will walk you through creating the following files with sensible defaults for your project:
  - .dockerignore
  - Dockerfile
  - compose.yaml
  - README.Docker.md

Let's get started!

? What application platform does your project use? ASP.NET Core
? What's the name of your solution's main project? myWebApp
? What version of .NET do you want to use? 10.0
? What local port do you want to use to access your server? 8080

In the following Dockerfile, the FROM instructions use dhi.io/dotnet:10-sdk and dhi.io/aspnetcore:10 as the base images.

Dockerfile

# syntax=docker/dockerfile:1

FROM --platform=$BUILDPLATFORM dhi.io/dotnet:10-sdk AS build
ARG TARGETARCH
COPY . /source
WORKDIR /source/src
RUN --mount=type=cache,id=nuget,target=/root/.nuget/packages \
    dotnet publish -a ${TARGETARCH/amd64/x64} --use-current-runtime --self-contained false -o /app

FROM dhi.io/aspnetcore:10
WORKDIR /app
COPY --from=build /app .
ENTRYPOINT ["dotnet", "myWebApp.dll"]

Note
DHI runtime images already run as a non-root user (nonroot, UID 65532), so there's no need to create a user or specify USER in your Dockerfile. This reduces the attack surface and simplifies your configuration.

You can use docker init to create the necessary Docker assets. Inside the docker-dotnet-sample directory, run the docker init command in a terminal. docker init provides some default configuration, but you'll need to answer a few questions about your application. Refer to the following example to answer the prompts from docker init and use the same answers for your prompts.

$ docker init
Welcome to the Docker Init CLI!

This utility will walk you through creating the following files with sensible defaults for your project:
  - .dockerignore
  - Dockerfile
  - compose.yaml
  - README.Docker.md

Let's get started!

? What application platform does your project use? ASP.NET Core
? What's the name of your solution's main project? myWebApp
? What version of .NET do you want to use? 10.0
? What local port do you want to use to access your server? 8080

This generates a Dockerfile using the official .NET 10 images from Microsoft Container Registry:

Dockerfile

# syntax=docker/dockerfile:1

FROM --platform=$BUILDPLATFORM mcr.microsoft.com/dotnet/sdk:10.0-alpine AS build
ARG TARGETARCH
COPY . /source
WORKDIR /source/src
RUN --mount=type=cache,id=nuget,target=/root/.nuget/packages \
    dotnet publish -a ${TARGETARCH/amd64/x64} --use-current-runtime --self-contained false -o /app

FROM mcr.microsoft.com/dotnet/aspnet:10.0-alpine AS final
WORKDIR /app
COPY --from=build /app .
ARG UID=10001
RUN adduser \
    --disabled-password \
    --gecos "" \
    --home "/nonexistent" \
    --shell "/sbin/nologin" \
    --no-create-home \
    --uid "${UID}" \
    appuser
USER appuser
ENTRYPOINT ["dotnet", "myWebApp.dll"]

You should now have the following contents in your docker-dotnet-sample directory.

├── docker-dotnet-sample/
│ ├── .git/
│ ├── src/
│ ├── .dockerignore
│ ├── compose.yaml
│ ├── Dockerfile
│ ├── README.Docker.md
│ └── README.md

To learn more about the files, see the following:

Run the application

Inside the docker-dotnet-sample directory, run the following command in a terminal.

$ docker compose up --build

Open a browser and view the application at http://localhost:8080. You should see a simple web application.

In the terminal, press ctrl+c to stop the application.

Run the application in the background

You can run the application detached from the terminal by adding the -d option. Inside the docker-dotnet-sample directory, run the following command in a terminal.

$ docker compose up --build -d

Open a browser and view the application at http://localhost:8080. You should see a simple web application.

In the terminal, run the following command to stop the application.

$ docker compose down

For more information about Compose commands, see the Compose CLI reference.

Summary

In this section, you learned how you can containerize and run your .NET application using Docker.

Related information:

Next steps

In the next section, you'll learn how you can develop your application using Docker containers.

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Containerize a .NET application