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How to use the ASP.NET Core Containerizer agent skill

Updated · written with AI from the project's own documentation and checked against our catalogue data

The containerize-aspnetcore skill is an instruction file for an AI agent that tells it how to package an ASP.NET Core (.NET) web project into a Linux Docker container image. It is written for developers who want a working Dockerfile and .dockerignore without writing them from scratch, and for teams moving existing .NET web apps into Docker. After this guide you will know what the skill does, how to install it, how to ask for it in plain language, and what to check before you trust the output.

ASP.NET Core Containerizergithub/awesome-copilot · MIT

Quick start

  1. 1Download and unzip the skill. Download the ZIP from this page and unzip it so the containerize-aspnetcore folder with SKILL.md sits in ~/.claude/skills/ or a project's .claude/skills/ folder.
  2. 2Or upload it in the Claude apps. In the Claude apps, open Settings → Capabilities → Skills and upload the skill.
  3. 3Make a natural request. Ask the agent to containerize your ASP.NET Core project and name the project or its .csproj file.
  4. 4Set optional details. Mention any non-default .NET version, Linux distribution, port, base image or health check endpoint.
  5. 5Review the generated files. Read the Dockerfile and .dockerignore, and check that base image tags match the TargetFramework in your .csproj.
  6. 6Build and test the image. Build the image with Docker on your machine and run it to confirm the app starts.
  7. 7Commit after review. Commit the changes only after you have checked them, since the skill edits project files.

What is an agent skill and what does this one do?

An agent skill is a folder containing a SKILL.md file with instructions that an AI agent reads when a task matches the skill. This one is published as skills/containerize-aspnetcore in the github/awesome-copilot repository under the MIT licence.

When the skill is active, the agent reads your .csproj file to find the TargetFramework, which gives the .NET version. It then picks an official mcr.microsoft.com/dotnet base image and writes a multi-stage Dockerfile. The build stage uses a .NET SDK image to copy the project files, restore NuGet packages, copy the source, and publish to /app/publish. The final stage uses a runtime image, sets the working directory to /app, runs as a non-root user by default ($APP_UID), and copies the published output in.

  • Creates a Dockerfile in the project root and a .dockerignore file that excludes bin/, obj/, .git/, .vs/ and similar folders.
  • Targets Linux containers, with Debian as the default distribution and Alpine, Ubuntu, Chiseled and Azure Linux (Mariner) as options.
  • Asks the agent to make application settings and connection strings readable from environment variables.
  • Asks the agent to create a progress.md file that tracks its changes with check marks.
  • Adds a HEALTHCHECK instruction using curl only if you provide a health check endpoint.

Install the skill

You can install the skill in one of three ways. Download the ZIP for this skill from this page and unzip it into your personal skills folder, ~/.claude/skills/, so it is available in every project. Or unzip it into a project's .claude/skills/ folder so it applies only to that project and can be shared with your team through version control.

If you use the Claude apps, you can instead upload the skill under Settings → Capabilities → Skills.

  • Personal install: unzip into ~/.claude/skills/ so the containerize-aspnetcore folder contains SKILL.md.
  • Project install: unzip into the project's .claude/skills/ folder.
  • Claude apps: upload it under Settings → Capabilities → Skills.

Ask for it with a natural request

You do not need a special command. Describe the job in plain language and name the project or its .csproj file. The agent should match your request to the skill's description, which is about containerizing an ASP.NET Core project with a Dockerfile and .dockerfile files.

The skill's settings are optional. If you say nothing about them, the defaults apply: .NET 8.0, the Debian distribution, a non-root user of $APP_UID, and ASPNETCORE_URLS set to http://+:8080. Mention anything that differs, such as a port, a base image or a distribution.

  • Containerize the ASP.NET Core project in src/Shop/Shop.csproj for Linux Docker.
  • Write a multi-stage Dockerfile for my .NET web app using Alpine and expose port 8080.
  • Containerize this ASP.NET Core API with Ubuntu base images and add a health check at /health.
  • Move our existing .NET web app into Docker, using the .NET 9.0 SDK and runtime.

Check what the agent produces

Expect the agent to create or edit a small set of files. The skill scopes changes to what containerization needs, so application code changes should be limited. It explicitly does not set up infrastructure, which it says is handled separately.

Review every change before you commit. Read the Dockerfile, confirm the base image tags match the .NET version in your .csproj, and build the image yourself with Docker to test it. The skill's own text states that generated Dockerfiles and base image tags should be checked by someone who knows the app.

  • Dockerfile and .dockerignore in the project root.
  • progress.md tracking the changes.
  • Edits to app configuration so settings can come from environment variables.
  • Optional HEALTHCHECK instruction if you supplied an endpoint.

Safety notes: scripts and network access

The skill does not run scripts and does not use the network itself, according to its listing. The skill's files consist of a single SKILL.md.

Building the image still needs network access. Docker must pull Microsoft .NET base images, and NuGet packages must be restored. The agent's environment and your Docker setup control that access, not the skill.

  • Requires Docker or a compatible container build tool to build and test the image.
  • Requires network access to pull Microsoft .NET base images and NuGet packages.
  • Because the agent edits your project files, use version control so you can see and revert changes.

Tips for better results

Fill in the settings that matter for your app, such as ports, extra system packages, native libraries, private NuGet feeds and volume paths. Settings you leave out fall back to defaults, which may not suit your project.

If you have a private NuGet feed, mention it so the agent copies NuGet.config and configures the feed. Keep the progress.md file as a record of what changed.

  • Name the .csproj path explicitly when your repository has several projects.
  • State the Linux distribution if you need Alpine or Chiseled images.
  • Ask the agent to explain each change so you can learn the Dockerfile structure.

What people use it for

  • Containerizing an existing ASP.NET Core web app so it runs in Docker on Linux.
  • Producing a multi-stage Dockerfile that keeps the runtime image smaller than the SDK build image.
  • Preparing a .NET API for Kubernetes-style hosting, where a container image is the deployment unit.
  • Adding a health check endpoint to a container image using curl.
  • Getting a checklist of container practices, such as a non-root user and environment-based configuration, applied to an existing project.

Frequently asked questions

Is the containerize-aspnetcore skill free?

The skill is published under the MIT licence in the github/awesome-copilot repository. The licence is listed on this page, so check the repository for the full terms.

What do I need to use this skill?

You need Docker or a compatible container build tool to build and test the image, an ASP.NET Core project with a .csproj file, and network access to pull Microsoft .NET base images and NuGet packages.

Does it work for non-.NET projects?

No. The skill only targets ASP.NET Core (.NET) applications. Other languages and frameworks are outside its scope.

Where do I install the skill?

Unzip the downloaded ZIP into ~/.claude/skills/ for personal use or into a project's .claude/skills/ folder. In the Claude apps, you can upload it under Settings → Capabilities → Skills.

Does the skill set up infrastructure or deploy my app?

No. The skill explicitly excludes infrastructure setup, which it says is assumed to be handled separately. It covers only the container files and the related changes to your project.

Why is my generated Dockerfile not building?

Check that the base image tags match your project's .NET version from the TargetFramework element, that Docker can reach the network to pull images, and that any system packages or native libraries you named exist for the chosen Linux distribution. Then rebuild and review the output with someone who knows the app.

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Our verdict

Use this skill if you are an ASP.NET Core developer or team who wants a sensible multi-stage Dockerfile and .dockerignore as a starting point, and you are comfortable reviewing and testing the result. Pick something else if your project is not ASP.NET Core, if you need full infrastructure or deployment automation, or if you need a production-ready image without expert review.

Download the skill