Dev Container — .NET

Overview

Configure a dev container for .NET development using the official dotnet feature. Supports multiple SDK versions, workloads, and integration with C# Dev Kit.

Dotnet Feature

{
  "features": {
    "ghcr.io/devcontainers/features/dotnet:2": {
      "version": "9.0",
      "additionalVersions": "8.0"
    }
  }
}

Feature Options

Option	Default	Description
version	latest	Primary .NET SDK version (9.0, 8.0, latest, none)
additionalVersions		Comma-separated extra SDK versions to install
workloads		Comma-separated .NET workloads (e.g., aspire, wasm-tools, maui)
installUsingApt	true	Use apt package manager when available

Install Workloads

{
  "features": {
    "ghcr.io/devcontainers/features/dotnet:2": {
      "version": "9.0",
      "workloads": "aspire, wasm-tools"
    }
  }
}

Full Example

{
  "name": ".NET 9 Development",
  "image": "mcr.microsoft.com/devcontainers/dotnet:9.0",
  "features": {
    "ghcr.io/devcontainers/features/github-cli:1": {}
  },
  "forwardPorts": [5000, 5001],
  "portsAttributes": {
    "5000": { "label": "HTTP", "onAutoForward": "notify" },
    "5001": { "label": "HTTPS", "onAutoForward": "notify" }
  },
  "postCreateCommand": "dotnet restore",
  "customizations": {
    "vscode": {
      "extensions": [
        "ms-dotnettools.csdevkit",
        "ms-dotnettools.csharp"
      ],
      "settings": {
        "dotnet.defaultSolution": "MyApp.sln"
      }
    }
  }
}

Using the Base Image vs Feature

Approach	When to Use
"image": "mcr.microsoft.com/devcontainers/dotnet:9.0"	.NET-only projects; comes preconfigured
Base image + ghcr.io/devcontainers/features/dotnet:2	Multi-language projects; compose with other features

NuGet Configuration

Mount a local NuGet config or set package sources via environment variables:

{
  "containerEnv": {
    "NUGET_PACKAGES": "/home/vscode/.nuget/packages",
    "DOTNET_CLI_TELEMETRY_OPTOUT": "1"
  },
  "mounts": [
    "source=${localEnv:HOME}/.nuget,target=/home/vscode/.nuget,type=bind,consistency=cached"
  ]
}

Multi-Project Solutions

For solutions with multiple projects, set the workspace folder and default solution:

{
  "workspaceFolder": "/workspace",
  "customizations": {
    "vscode": {
      "settings": {
        "dotnet.defaultSolution": "src/MyApp.sln",
        "omnisharp.enableMsBuildLoadProjectsOnDemand": true
      }
    }
  },
  "postCreateCommand": "dotnet restore src/MyApp.sln"
}

Best Practices

• Use the dedicated mcr.microsoft.com/devcontainers/dotnet image for .NET-only projects — it includes the SDK, runtime, and common tools.
• Use the dotnet feature on a base image when you need .NET alongside other languages.
• Pin to a major SDK version (9.0, 8.0) rather than latest for reproducibility.
• Install workloads via the feature's workloads option rather than in postCreateCommand so they are cached in prebuilds.
• Add ms-dotnettools.csdevkit for full IDE experience (solution explorer, test explorer, refactoring).
• Set DOTNET_CLI_TELEMETRY_OPTOUT=1 in containerEnv for CI-like environments.
• Forward ports 5000/5001 for Kestrel HTTP/HTTPS and use portsAttributes for auto-open behavior.