Project Type Detection

Project Type Detection

This page documents the detection mechanics behind the policy described in Engineering Principles.

During Sdk.props evaluation the SDK classifies every .csproj by reading the project filename, the Sdk attribute, and on-disk markers. The resulting flags drive the defaults described throughout this wiki.

Detection flags

Flag	Condition
IsCSharpProject	Project file extension is .csproj.
IsTestProject	Project name matches `^.*.([\w
IsSharedTestingProject	Project name is one of SharedTestingFramework, SharedTestingInfrastructure, SharedTestingInfra, SharedTestingUtilities, SharedTestingUtils, SharedTestingLibrary, SharedTestingLib, SharedTestingHelpers.
IsSharedProject	Project name is one of Shared, SharedFramework, SharedInfrastructure, SharedInfra, SharedUtilities, SharedUtils, SharedLibrary, SharedLib, SharedHelpers.
IsContainerProject	A Dockerfile, dockerfile, or Dockerfile.dev exists in the project directory.
IsSdkProject	An Sdk value is parsed from the <Project>/<Import> element.
IsWebSdkProject	SdkProjectName is Microsoft.NET.Sdk.Web.
IsWorkerSdkProject	SdkProjectName is Microsoft.NET.Sdk.Worker.
IsAspireHostProject	SdkProjectName starts with Aspire.Sdk.Host or Aspire.AppHost.Sdk.
IsCLIProject	Project name ends with CLI, Console, CommandLine, QuickStart, or QuickStarts.
IsBlazorWebAssemblyProject	SdkProjectName is Microsoft.NET.Sdk.BlazorWebAssembly.
IsRazorClassLibraryProject	SdkProjectName is Microsoft.NET.Sdk.Razor.
IsBffProject	A web SDK project whose name ends with Bff (case-sensitive), or that sets IsBffProject=true. IsBffProject=false opts out.
IsBlazorHostProject	A web SDK project that references an IsBlazorWebAssemblyProject project - at evaluation for the <Name>/<Name>.Client pairing, during the build (ResolvePurviewBlazorHostProject) otherwise. Never implies IsBffProject.
IsRoslynComponent	<IsRoslynComponent>true</IsRoslynComponent> is declared in the project file.
IsPackable	<IsPackable>true</IsPackable> is declared in the project file.
IsWebProject	Marker used in SDK web-project behaviour.

TestingType is the detected test category suffix from the project name (for example Unit, Integration, E2E); TargetProjectName is the inferred non-test project name that a test project targets. The detected TestingType also becomes the baseline test category, while additional categories remain available to the test suite.

Detection is a pattern, not a lookup against the set below. A project named MyProject.GoldenTests is detected, and gets TestingType=Golden and Category=Golden, even though Golden appears nowhere in the SDK. The pattern requires the dot, so a project named plainly UnitTests is not detected as a test project at all — it gets no runner, no coverage and no category.

The TestType item group below governs InternalsVisibleTo generation instead: a non-test project grants access to {AssemblyName}.{TestType}Tests for each name on it. A suffix outside the set still builds, still runs and still gets its category — it just cannot reach the target project’s internal members.

The SDK ships the following full TestType set, in addition to the standard Unit and Integration values: Acceptance, Accessibility, Approval, Architecture, Benchmark, BlackBox, Capacity, Chaos, Compatibility, Compliance, Component, Concurrency, Configuration, Contract, Deployment, E2E, EndToEnd, Endurance, Environment, Failover, Functional, Fuzz, Globalization, GrayBox, GreyBox, Integration, Interactive, Interoperability, Load, Localization, Migration, Mutation, Penetration, Performance, Property, Recovery, Regression, Resilience, Sanity, Scenario, Security, Smoke, Snapshot, Soak, Spike, Stress, System, Threat, Unit, Upgrade, Usability, Visual, and WhiteBox.

What each type gets

Test projects (IsTestProject=true)

• OutputType=Exe when the testing framework is not None.
• A test-context rule set (PurviewTestContextNoWarn): the production API-surface rules (CA1002, CA1012, CA1034, CA1047, CA1050, CA1051, CA1062, CA1064, CA1515, CA1707) are exempt, while the strict style contract (IDE0040, field naming, formatting, IDE1006 naming rules) still applies. DisablePurviewTestContextRuleSet=true enforces the production rules instead.
• CollectCoverage=true with coverage exclusions for framework and mocking packages.
• IsPackable=false, IsPublishable=false, MaxCpuCount=0.
• Disabled native instrumentation by default.
• An [assembly: ExcludeFromCodeCoverage] attribute.
• Automatic ProjectReference to the target project (resolved as ../<TargetProjectName>/, sibling src/ paths, and the shared testing project alongside).
• A [Category: <TestingType>] assembly attribute (TUnit) or [Trait("Category", ...)] (Xunit).

Shared testing projects (IsSharedTestingProject=true)

• Test package references, but not the test runner or coverage settings.
• A [Skip] attribute (TUnit) so the shared assembly is never executed directly.
• TUnit.Core instead of the full TUnit package.
• OutputType=Library with IsTestProject/IsTestingPlatformApplication cleared, reasserted after the package props (which otherwise flip the project into an executable test host). The fixtures are consumed by the test assemblies, so staying a library avoids CA1515 (which only targets executables). Set PurviewSharedTestingOutputType=Exe before the SDK import to keep the package-driven test-host shape.

Shared projects (IsSharedProject=true)

• Automatically referenced by sibling non-test projects via wildcard (../Shared*/Shared*.csproj); test projects automatically reference ../SharedTesting*/SharedTesting*.csproj.

Container projects

• InvariantGlobalization=true, PublishAot=true, DockerDefaultTargetOS=Linux, DockerfileContext=..\..\.
• Adds Microsoft.VisualStudio.Azure.Containers.Tools.Targets.

Web SDK projects (IsWebSdkProject=true)

• Non-API web apps get InterceptorsNamespaces extended with Microsoft.AspNetCore.OpenApi.Generated for OpenAPI interceptors.

CLI projects

• OutputType=Exe, appsettings*.json copied to the output directory.
• CA1515 suppressed (nested settings classes on internal commands).

Aspire host projects

• OutputType=Exe (when not a test/shared-testing project), CA1515 suppressed.

Blazor WebAssembly clients (IsBlazorWebAssemblyProject=true)

• IsPackable=false unless the project sets it, no container defaults even with a Dockerfile, and no automatic ../Shared* reference. DisablePurviewBlazorWebAssemblyDefaults=true (before the SDK import) restores the generic defaults.
• PRBLZ0001 for each ProjectReference that does not set PurviewBrowserSafe.
• Globalisation, trimming and the Blazor runtime settings are left to the Blazor SDK.

Blazor hosts (IsBlazorHostProject=true)

• A host named <Name> gets an automatic reference to its <Name>.Client client unless it declares one. PurviewAutoBlazorClientReference=false opts out.

BFF hosts (IsBffProject=true)

• No packages added. No OpenAPI interceptor namespace unless the BFF references Microsoft.AspNetCore.OpenApi or sets PurviewBffExposesApi=true.
• PDS0008/PDS0009 on the authentication cookie (see Analyzers).

Browser-safe libraries (PurviewBrowserSafe=true)

• IsAotCompatible=true, <SupportedPlatform Include="browser" />, and the trim, single-file, AOT and CA1416 ids in WarningsAsErrors - each only where the project set nothing. PurviewBrowserSafeWarningsAsErrors=false keeps them as warnings.
• The same PRBLZ0001 reference check a client runs.

The README’s Blazor WebAssembly and BFF section has the failure each behaviour prevents.

Roslyn components (IsRoslynComponent=true)

• Default netstandard2.0 target, LangVersion=latest, Nullable=enable, TreatWarningsAsErrors=true, EnforceExtendedAnalyzerRules=true, Deterministic=true.
• Compiler-generated output under the intermediate directory, no dependency file.
• No symbol package by default; the PDB ships beside the analyzer in the package.
• SourceLink with EmbedUntrackedSources=true, telemetry excluded.
• See Packaging for how the analyzer assets are packed.

Packable projects (IsPackable=true)

• GenerateDocumentationFile, IncludeSource, IncludeSymbols (.snupkg), PublishRepositoryUrl, EmbedUntrackedSources, DebugType=portable defaults.
• See Packaging.

Properties exposed to the compiler

The detection flags (plus many SDK properties) are exposed to Roslyn analyzers and source generators via CompilerVisibleProperty, readable as build_property.<PropertyName>. The full list is in the Configuration Reference.