.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

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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