dotnet-project-structure

SKILL.md

.NET Project Structure and Build Configuration

When to Use This Skill

Use this skill when:

Setting up a new .NET solution with modern best practices

Configuring centralized build properties across multiple projects

Implementing central package version management

Setting up SourceLink for debugging and NuGet packages

Automating version management with release notes

Pinning SDK versions for consistent builds

Related Skills

dotnet-local-tools - Managing local .NET tools with dotnet-tools.json

microsoft-extensions-configuration - Configuration validation patterns

Solution File Format (.slnx)

The .slnx format is the modern XML-based solution file format introduced in .NET 9. It replaces the traditional .sln format.

Benefits Over Traditional .sln

Aspect
.sln (Legacy)
.slnx (Modern)

Format
Custom text format
Standard XML

Readability
GUIDs, cryptic syntax
Clean, human-readable

Version control
Hard to diff/merge
Easy to diff/merge

Editing
IDE required
Any text editor

Version Requirements

Tool
Minimum Version

.NET SDK
9.0.200

Visual Studio
17.13

MSBuild
Visual Studio Build Tools 17.13

Note: Starting with .NET 10, dotnet new sln creates .slnx files by default. In .NET 9, you must explicitly migrate or specify the format.

Example .slnx File

<Solution>
  <Folder Name="/build/">
    <File Path="Directory.Build.props" />
    <File Path="Directory.Packages.props" />
    <File Path="global.json" />
    <File Path="NuGet.Config" />
    <File Path="README.md" />
  </Folder>
  <Folder Name="/src/">
    <Project Path="src/MyApp/MyApp.csproj" />
    <Project Path="src/MyApp.Core/MyApp.Core.csproj" />
  </Folder>
  <Folder Name="/tests/">
    <Project Path="tests/MyApp.Tests/MyApp.Tests.csproj" />
  </Folder>
</Solution>

Migrating from .sln to .slnx

Use the dotnet sln migrate command to convert existing solutions:

# Migrate a specific solution file
dotnet sln MySolution.sln migrate

# Or if only one .sln exists in the directory, just run:
dotnet sln migrate

Important: Do not keep both .sln and .slnx files in the same repository. This causes issues with automatic solution detection and can lead to sync problems. After migration, delete the old .sln file.

You can also migrate in Visual Studio:

Open the solution

Select the Solution in Solution Explorer

Go to File > Save Solution As...

Change "Save as type" to Xml Solution File (*.slnx)

Creating a New .slnx Solution

# .NET 10+: Creates .slnx by default
dotnet new sln --name MySolution

# .NET 9: Specify the format explicitly
dotnet new sln --name MySolution --format slnx

# Add projects (works the same for both formats)
dotnet sln add src/MyApp/MyApp.csproj

Recommendation

If you're using .NET 9.0.200 or later, migrate your solutions to .slnx. The benefits are significant:

Dramatically fewer merge conflicts (no random GUIDs changing)

Human-readable and editable in any text editor

Consistent with modern .csproj format

Better diff/review experience in pull requests

Directory.Build.props

Directory.Build.props provides centralized build configuration that applies to all projects in a directory tree. Place it at the solution root.

Complete Example

<Project>
  <!-- Metadata -->
  <PropertyGroup>
    <Authors>Your Team</Authors>
    <Company>Your Company</Company>
    <!-- Dynamic copyright year - updates automatically -->
    <Copyright>Copyright © 2020-$([System.DateTime]::Now.Year) Your Company</Copyright>
    <Product>Your Product</Product>
    <PackageProjectUrl>https://github.com/yourorg/yourrepo</PackageProjectUrl>
    <RepositoryUrl>https://github.com/yourorg/yourrepo</RepositoryUrl>
    <PackageLicenseExpression>Apache-2.0</PackageLicenseExpression>
    <PackageTags>your;tags;here</PackageTags>
  </PropertyGroup>

  <!-- C# Language Settings -->
  <PropertyGroup>
    <LangVersion>latest</LangVersion>
    <Nullable>enable</Nullable>
    <ImplicitUsings>enable</ImplicitUsings>
    <TreatWarningsAsErrors>true</TreatWarningsAsErrors>
    <NoWarn>$(NoWarn);CS1591</NoWarn> <!-- Missing XML comments -->
  </PropertyGroup>

  <!-- Version Management -->
  <PropertyGroup>
    <VersionPrefix>1.0.0</VersionPrefix>
    <PackageReleaseNotes>See RELEASE_NOTES.md</PackageReleaseNotes>
  </PropertyGroup>

  <!-- Target Framework Definitions (reusable properties) -->
  <PropertyGroup>
    <NetStandardLibVersion>netstandard2.0</NetStandardLibVersion>
    <NetLibVersion>net8.0</NetLibVersion>
    <NetTestVersion>net9.0</NetTestVersion>
  </PropertyGroup>

  <!-- SourceLink Configuration -->
  <PropertyGroup>
    <PublishRepositoryUrl>true</PublishRepositoryUrl>
    <EmbedUntrackedSources>true</EmbedUntrackedSources>
    <IncludeSymbols>true</IncludeSymbols>
    <SymbolPackageFormat>snupkg</SymbolPackageFormat>
  </PropertyGroup>

  <ItemGroup>
    <PackageReference Include="Microsoft.SourceLink.GitHub" PrivateAssets="All" />
  </ItemGroup>

  <!-- NuGet Package Assets -->
  <ItemGroup>
    <None Include="$(MSBuildThisFileDirectory)logo.png" Pack="true" PackagePath="\" />
    <None Include="$(MSBuildThisFileDirectory)README.md" Pack="true" PackagePath="\" />
  </ItemGroup>

  <PropertyGroup>
    <PackageIcon>logo.png</PackageIcon>
    <PackageReadmeFile>README.md</PackageReadmeFile>
  </PropertyGroup>

  <!-- Global Using Statements -->
  <ItemGroup>
    <Using Include="System.Collections.Immutable" />
  </ItemGroup>
</Project>

Key Patterns

Dynamic Copyright Year

<Copyright>Copyright © 2020-$([System.DateTime]::Now.Year) Your Company</Copyright>

Uses MSBuild property functions to insert current year at build time. No manual updates needed.

Reusable Target Framework Properties

Define target frameworks once, reference everywhere:

<!-- In Directory.Build.props -->
<PropertyGroup>
  <NetLibVersion>net8.0</NetLibVersion>
  <NetTestVersion>net9.0</NetTestVersion>
</PropertyGroup>

<!-- In MyApp.csproj -->
<PropertyGroup>
  <TargetFramework>$(NetLibVersion)</TargetFramework>
</PropertyGroup>

<!-- In MyApp.Tests.csproj -->
<PropertyGroup>
  <TargetFramework>$(NetTestVersion)</TargetFramework>
</PropertyGroup>

SourceLink for NuGet Packages

SourceLink enables step-through debugging of NuGet packages:

<PropertyGroup>
  <PublishRepositoryUrl>true</PublishRepositoryUrl>
  <EmbedUntrackedSources>true</EmbedUntrackedSources>
  <IncludeSymbols>true</IncludeSymbols>
  <SymbolPackageFormat>snupkg</SymbolPackageFormat>
</PropertyGroup>

<ItemGroup>
  <!-- Choose the right provider for your source control -->
  <PackageReference Include="Microsoft.SourceLink.GitHub" PrivateAssets="All" />
  <!-- Or: Microsoft.SourceLink.AzureRepos.Git -->
  <!-- Or: Microsoft.SourceLink.GitLab -->
  <!-- Or: Microsoft.SourceLink.Bitbucket.Git -->
</ItemGroup>

Directory.Packages.props - Central Package Management

Central Package Management (CPM) provides a single source of truth for all NuGet package versions.

Setup

<Project>
  <PropertyGroup>
    <ManagePackageVersionsCentrally>true</ManagePackageVersionsCentrally>
  </PropertyGroup>

  <!-- Define version variables for related packages -->
  <PropertyGroup>
    <AkkaVersion>1.5.35</AkkaVersion>
    <AspireVersion>9.1.0</AspireVersion>
  </PropertyGroup>

  <!-- Application Dependencies -->
  <ItemGroup Label="App Dependencies">
    <PackageVersion Include="Akka" Version="$(AkkaVersion)" />
    <PackageVersion Include="Akka.Cluster" Version="$(AkkaVersion)" />
    <PackageVersion Include="Akka.Persistence" Version="$(AkkaVersion)" />
    <PackageVersion Include="Microsoft.Extensions.Hosting" Version="9.0.0" />
  </ItemGroup>

  <!-- Build/Tooling Dependencies -->
  <ItemGroup Label="Build Dependencies">
    <PackageVersion Include="Microsoft.SourceLink.GitHub" Version="8.0.0" />
  </ItemGroup>

  <!-- Test Dependencies -->
  <ItemGroup Label="Test Dependencies">
    <PackageVersion Include="xunit" Version="2.9.3" />
    <PackageVersion Include="xunit.runner.visualstudio" Version="3.0.1" />
    <PackageVersion Include="FluentAssertions" Version="7.0.0" />
    <PackageVersion Include="Microsoft.NET.Test.Sdk" Version="17.12.0" />
    <PackageVersion Include="coverlet.collector" Version="6.0.3" />
  </ItemGroup>
</Project>

Consuming Packages (No Version Needed)

<!-- In MyApp.csproj -->
<ItemGroup>
  <PackageReference Include="Akka" />
  <PackageReference Include="Akka.Cluster" />
  <PackageReference Include="Microsoft.Extensions.Hosting" />
</ItemGroup>

<!-- In MyApp.Tests.csproj -->
<ItemGroup>
  <PackageReference Include="xunit" />
  <PackageReference Include="FluentAssertions" />
  <PackageReference Include="Microsoft.NET.Test.Sdk" />
</ItemGroup>

Benefits

Single source of truth - All versions in one file

No version drift - All projects use same versions

Easy updates - Change once, applies everywhere

Grouped packages - Version variables for related packages (e.g., all Akka packages)

global.json - SDK Version Pinning

Pin the .NET SDK version for consistent builds across all environments.

{
  "sdk": {
    "version": "9.0.200",
    "rollForward": "latestFeature"
  }
}

Roll Forward Policies

Policy
Behavior

disable
Exact version required

patch
Same major.minor, latest patch

feature
Same major, latest minor.patch

latestFeature
Same major, latest feature band

minor
Same major, latest minor

latestMinor
Same major, latest minor

major
Latest SDK (not recommended)

Recommended: latestFeature - Allows patch updates within the same feature band.

Version Management with RELEASE_NOTES.md

Release Notes Format

#### 1.2.0 January 15th 2025 ####

- Added new feature X
- Fixed bug in Y
- Improved performance of Z

#### 1.1.0 December 10th 2024 ####

- Initial release with features A, B, C

Parsing Script (getReleaseNotes.ps1)

function Get-ReleaseNotes {
    param (
        [Parameter(Mandatory=$true)]
        [string]$MarkdownFile
    )

    $content = Get-Content -Path $MarkdownFile -Raw
    $sections = $content -split "####"

    $result = [PSCustomObject]@{
        Version      = $null
        Date         = $null
        ReleaseNotes = $null
    }

    if ($sections.Count -ge 3) {
        $header = $sections[1].Trim()
        $releaseNotes = $sections[2].Trim()

        $headerParts = $header -split " ", 2
        if ($headerParts.Count -eq 2) {
            $result.Version = $headerParts[0]
            $result.Date = $headerParts[1]
        }

        $result.ReleaseNotes = $releaseNotes
    }

    return $result
}

Version Bump Script (bumpVersion.ps1)

function UpdateVersionAndReleaseNotes {
    param (
        [Parameter(Mandatory=$true)]
        [PSCustomObject]$ReleaseNotesResult,
        [Parameter(Mandatory=$true)]
        [string]$XmlFilePath
    )

    $xmlContent = New-Object XML
    $xmlContent.Load($XmlFilePath)

    # Update VersionPrefix
    $versionElement = $xmlContent.SelectSingleNode("//VersionPrefix")
    $versionElement.InnerText = $ReleaseNotesResult.Version

    # Update PackageReleaseNotes
    $notesElement = $xmlContent.SelectSingleNode("//PackageReleaseNotes")
    $notesElement.InnerText = $ReleaseNotesResult.ReleaseNotes

    $xmlContent.Save($XmlFilePath)
}

Build Script (build.ps1)

# Load helper scripts
. "$PSScriptRoot\scripts\getReleaseNotes.ps1"
. "$PSScriptRoot\scripts\bumpVersion.ps1"

# Parse release notes and update Directory.Build.props
$releaseNotes = Get-ReleaseNotes -MarkdownFile (Join-Path -Path $PSScriptRoot -ChildPath "RELEASE_NOTES.md")
UpdateVersionAndReleaseNotes -ReleaseNotesResult $releaseNotes -XmlFilePath (Join-Path -Path $PSScriptRoot -ChildPath "Directory.Build.props")

Write-Output "Updated to version $($releaseNotes.Version)"

CI/CD Integration

# GitHub Actions example
- name: Update version from release notes
  shell: pwsh
  run: ./build.ps1

- name: Build
  run: dotnet build -c Release

- name: Pack with tag version
  run: dotnet pack -c Release /p:PackageVersion=${{ github.ref_name }}

- name: Push to NuGet
  run: dotnet nuget push **/*.nupkg --api-key ${{ secrets.NUGET_API_KEY }} --source https://api.nuget.org/v3/index.json

NuGet.Config

Configure NuGet sources and behavior:

<?xml version="1.0" encoding="utf-8"?>
<configuration>
  <solution>
    <add key="disableSourceControlIntegration" value="true" />
  </solution>

  <packageSources>
    <clear />
    <add key="nuget.org" value="https://api.nuget.org/v3/index.json" />
    <!-- Add private feeds if needed -->
    <!-- <add key="MyCompany" value="https://pkgs.dev.azure.com/myorg/_packaging/myfeed/nuget/v3/index.json" /> -->
  </packageSources>
</configuration>

Key Settings:

<clear /> - Remove inherited/default sources for reproducible builds

disableSourceControlIntegration - Prevents TFS/Git integration issues

Complete Project Structure

MySolution/
├── .config/
│   └── dotnet-tools.json           # Local .NET tools
├── .github/
│   └── workflows/
│       ├── pr-validation.yml       # PR checks
│       └── release.yml             # NuGet publishing
├── scripts/
│   ├── getReleaseNotes.ps1         # Parse RELEASE_NOTES.md
│   └── bumpVersion.ps1             # Update Directory.Build.props
├── src/
│   ├── MyApp/
│   │   └── MyApp.csproj
│   └── MyApp.Core/
│       └── MyApp.Core.csproj
├── tests/
│   └── MyApp.Tests/
│       └── MyApp.Tests.csproj
├── Directory.Build.props           # Centralized build config
├── Directory.Packages.props        # Central package versions
├── MySolution.slnx                 # Modern solution file
├── global.json                     # SDK version pinning
├── NuGet.Config                    # Package source config
├── build.ps1                       # Build orchestration
├── RELEASE_NOTES.md                # Version history
├── README.md                       # Project documentation
└── logo.png                        # Package icon

Quick Reference

File
Purpose

MySolution.slnx
Modern XML solution file

Directory.Build.props
Centralized build properties

Directory.Packages.props
Central package version management

global.json
SDK version pinning

NuGet.Config
Package source configuration

RELEASE_NOTES.md
Version history (parsed by build)

build.ps1
Build orchestration script

.config/dotnet-tools.json
Local .NET tools