.NET Solution & Project Setup

Targets .NET 9 SDK (9.0.200+) and later, where noted.

Solution File

• Use .slnx (XML solution format), not .sln. Default for dotnet new sln since .NET 10 SDK; available since 9.0.200.
• Migrate an existing solution: dotnet sln migrate (creates .slnx, keeps .sln untouched).
• Create new: dotnet new sln (or --format sln to opt back out).

Repository Root Checklist

File	Purpose
<Name>.slnx	solution definition
.editorconfig	code style + analyzer severities, enforced at build via EnforceCodeStyleInBuild
Directory.Build.props	MSBuild properties shared by every project
Directory.Packages.props	central package management (CPM) — package versions in one place
global.json	pin SDK version (rollForward: latestMinor)
.gitattributes	enforce line endings (* text=auto eol=lf) for deterministic diffs
NuGet.config	package sources; add source mapping to silence NU1507 when using CPM with >1 source
.config/dotnet-tools.json	local tool manifest (dotnet tool restore)

Directory.Build.props — Required Properties

Property	Value	Why
TargetFramework	e.g. net10.0	single source of truth for the whole repo
LangVersion	latest	newest C# features as soon as the SDK supports them
Nullable	enable	nullable reference type analysis
ImplicitUsings	enable	drop boilerplate using directives
TreatWarningsAsErrors	true	fail the build instead of accumulating warnings
EnforceCodeStyleInBuild	true	.editorconfig IDE0xxx style rules run on dotnet build, not just in the IDE
Deterministic	true	byte-identical assemblies for identical inputs (default true already, set explicitly)
EnableNETAnalyzers	true	run the built-in CAxxxx code-quality analyzers

Full example + extra hardening properties (AnalysisLevel, AnalysisMode, test-project overrides, versioning) → references/directory-build-props.md.

SourceLink

Every packable/publishable project needs SourceLink so consumers can step into source while debugging:

<PropertyGroup>
  <PublishRepositoryUrl>true</PublishRepositoryUrl>
  <EmbedUntrackedSources>true</EmbedUntrackedSources>
  <DebugType>portable</DebugType>
  <ContinuousIntegrationBuild Condition="'$(CI)' == 'true'">true</ContinuousIntegrationBuild>
</PropertyGroup>
<ItemGroup>
  <PackageReference Include="Microsoft.SourceLink.GitHub" Version="8.0.0" PrivateAssets="All" />
</ItemGroup>

ContinuousIntegrationBuild must only be true on CI (it maps local paths to repo-relative paths); leaving it true locally breaks the "Just My Code" experience. Details, symbol packages, alternate providers → references/directory-build-props.md.

Central Package Management

Directory.Packages.props sets ManagePackageVersionsCentrally=true and declares <PackageVersion> items; every project's <PackageReference> then omits Version. Full setup, GlobalPackageReference, transitive pinning, override rules → references/central-package-management.md.

Reference Files

File	Load When
references/directory-build-props.md	Writing the full Directory.Build.props, SourceLink details, analyzer levels, test-project overrides, git-based versioning
references/central-package-management.md	Writing Directory.Packages.props, GlobalPackageReference, transitive pinning, package source mapping
references/repo-scaffold.md	.slnx migration, .editorconfig, global.json, .gitattributes, local tool manifest, CI formatting checks