Item Management

by dotnet0608d8924cd3MIT5.5K starsListed Oct 8, 2026Updated Oct 8, 2026Repository updated today

Own concrete MSBuild ItemGroup and item-expression questions. USE FOR: Include, Remove, Update, item identity and metadata, transforms, filtering, batching, duplicate or overlapping items, and reviews that verify whether those operations are correct. Generated items stay in scope when the central defect is item identity, metadata, batching, duplicate declarations, or glob/Remove/Update semantics. For a generated artifact missing from compilation or output, wrong target timing/path, or FileWrites clean tracking without a broader item-semantics defect, use including-generated-files. The item operation may be broken, suspected, or already correct. Exclude property-only issues, general incrementality with no item question, broad reviews with no concrete item concern, and non-MSBuild systems.

Instructions onlySoftware Development

AI-generated overview

Guides MSBuild ItemGroup work: Include, Remove, Update, metadata, transforms, batching and duplicate items.

What it does: This skill provides canonical MSBuild item-management patterns drawn from Microsoft.Common.CurrentVersion.targets. It explains the Include, Remove and Update operations, item identity and metadata, transforms, Exclude patterns, conditional inclusion, and batching with %(Metadata). It also lists common pitfalls such as cross-product batching, generated files in the source tree, and missing FileWrites entries.
When to use it: Use it for concrete MSBuild ItemGroup or item-expression questions, including reviews that verify whether item operations are correct. It fits issues involving item identity, metadata, batching, duplicate or overlapping items, and glob, Remove or Update semantics. It is not for property-only issues, general incrementality without an item question, or non-MSBuild systems.
Requirements: No scripts or tools are required; it is an instructions-only reference. The agent needs no packages, credentials or network access.

MSBuild Item Management Patterns

Canonical patterns for working with item groups, from Microsoft.Common.CurrentVersion.targets.

Include / Remove / Update — Three Operations

Operation	Purpose	When to use
`Include`	Add new items to the group	Creating items with identity + metadata
`Remove`	Remove items matching a pattern	Excluding files or clearing a group
`Update`	Modify metadata on existing items	Adding/changing metadata without re-adding

Include — Add Items

Remove — Subtract Items

xml

<ItemGroup>  <!-- Remove specific items -->  <Reference Remove="$(AdditionalExplicitAssemblyReferences)" />
  <!-- Set subtraction: prior minus current -->  <_CleanOrphanFileWrites Include="@(_CleanPriorFileWrites)"      Exclude="@(_CleanCurrentFileWrites)" />
  <!-- Clear an entire group -->  <_Temporary Remove="@(_Temporary)" /></ItemGroup>

<ItemGroup>  <!-- Remove specific items -->  <Reference Remove="$(AdditionalExplicitAssemblyReferences)" />
  <!-- Set subtraction: prior minus current -->  <_CleanOrphanFileWrites Include="@(_CleanPriorFileWrites)"      Exclude="@(_CleanCurrentFileWrites)" />
  <!-- Clear an entire group -->  <_Temporary Remove="@(_Temporary)" /></ItemGroup>

Update — Modify Existing Items

xml

<ItemGroup>  <EmbeddedResource Update="@(EmbeddedResource)"      Condition="'%(NuGetPackageId)' == 'Microsoft.CodeAnalysis.Collections'">    <GenerateSource>true</GenerateSource>    <ClassName>Microsoft.CodeAnalysis.Collections.SR</ClassName>  </EmbeddedResource></ItemGroup>

<ItemGroup>  <EmbeddedResource Update="@(EmbeddedResource)"      Condition="'%(NuGetPackageId)' == 'Microsoft.CodeAnalysis.Collections'">    <GenerateSource>true</GenerateSource>    <ClassName>Microsoft.CodeAnalysis.Collections.SR</ClassName>  </EmbeddedResource></ItemGroup>

Update does not add items — it only modifies items already in the group.

Item Batching — %(Metadata)

When %(Metadata) appears in target attributes or task parameters, MSBuild batches execution per unique metadata value.

Target-level batching (Outputs)

xml

<Target Name="GenerateSatelliteAssemblies"    Inputs="$(MSBuildAllProjects);@(_SatelliteAssemblyResourceInputs)"    Outputs="$(IntermediateOutputPath)%(Culture)\$(TargetName).resources.dll">  <!-- Runs once per unique Culture value --></Target>

<Target Name="GenerateSatelliteAssemblies"    Inputs="$(MSBuildAllProjects);@(_SatelliteAssemblyResourceInputs)"    Outputs="$(IntermediateOutputPath)%(Culture)\$(TargetName).resources.dll">  <!-- Runs once per unique Culture value --></Target>

Task-level batching

xml

<Copy SourceFiles="@(_SourceItems)"    DestinationFiles="@(_SourceItems->'$(OutDir)%(TargetPath)')"></Copy>

<Copy SourceFiles="@(_SourceItems)"    DestinationFiles="@(_SourceItems->'$(OutDir)%(TargetPath)')"></Copy>

Per-item filtering with Condition

xml

<ItemGroup>  <_ResxOutput Include="@(EmbeddedResource->'%(OutputResource)')"      Condition="'%(EmbeddedResource.WithCulture)' == 'false'" /></ItemGroup>

<ItemGroup>  <_ResxOutput Include="@(EmbeddedResource->'%(OutputResource)')"      Condition="'%(EmbeddedResource.WithCulture)' == 'false'" /></ItemGroup>

Batching rules

%(Metadata) in Condition or Outputs → target batches per unique value.
%(Metadata) in task parameters → task batches per unique value.
Do not mix %() from different item groups in the same expression — this causes a cross-product (see Common Pitfalls).

Item Transforms — @(Item->'expression')

Transforms create new item lists by applying an expression to each item:

xml

<!-- Transform file paths to destinations --><Copy SourceFiles="@(IntermediateAssembly)"    DestinationFiles="@(IntermediateAssembly->'$(OutDir)%(Filename)%(Extension)')"/>
<!-- Transform with separator for display --><Message Text="Files: @(Compile->'%(Filename)', ', ')" />

<!-- Transform file paths to destinations --><Copy SourceFiles="@(IntermediateAssembly)"    DestinationFiles="@(IntermediateAssembly->'$(OutDir)%(Filename)%(Extension)')"/>
<!-- Transform with separator for display --><Message Text="Files: @(Compile->'%(Filename)', ', ')" />

Exclude Pattern — Set Subtraction on Include

Exclude only works on Include — it cannot be used with Update or Remove.

Conditional Item Inclusion

xml

<!-- Condition on ItemGroup — all or nothing --><ItemGroup Condition="'$(NetCoreBuild)' == 'true'">  <PackageReference Include="System.IO.Pipelines" /></ItemGroup>
<!-- Condition on individual items --><ItemGroup>  <PackageReference Include="System.IO.Pipelines"      Condition="'$(NetCoreBuild)' == 'true'" /></ItemGroup>

<!-- Condition on ItemGroup — all or nothing --><ItemGroup Condition="'$(NetCoreBuild)' == 'true'">  <PackageReference Include="System.IO.Pipelines" /></ItemGroup>
<!-- Condition on individual items --><ItemGroup>  <PackageReference Include="System.IO.Pipelines"      Condition="'$(NetCoreBuild)' == 'true'" /></ItemGroup>

PrivateAssets on Tool/Analyzer Packages

xml

<ItemGroup>  <PackageReference Include="Microsoft.CodeAnalysis.NetAnalyzers" PrivateAssets="all" />  <PackageReference Include="StyleCop.Analyzers" PrivateAssets="all" /></ItemGroup>

<ItemGroup>  <PackageReference Include="Microsoft.CodeAnalysis.NetAnalyzers" PrivateAssets="all" />  <PackageReference Include="StyleCop.Analyzers" PrivateAssets="all" /></ItemGroup>

Common Pitfalls

Cross-product batching

Referencing %(Metadata) from two different item groups creates O(N×M) executions:

xml

<!-- BAD: Cross-product of @(Source) × @(Config) --><Exec Command="process %(Source.Identity) with %(Config.Identity)" />
<!-- GOOD: Reference one group via batching, the other via property --><Exec Command="process %(Source.Identity) with $(ConfigFile)" />

<!-- BAD: Cross-product of @(Source) × @(Config) --><Exec Command="process %(Source.Identity) with %(Config.Identity)" />
<!-- GOOD: Reference one group via batching, the other via property --><Exec Command="process %(Source.Identity) with $(ConfigFile)" />

Generated files in source tree

Write to $(IntermediateOutputPath) (obj/), not the source directory. Source-tree generation pollutes version control and can cause duplicate compilation via globs.

Missing FileWrites

Every file created during a target must be added to @(FileWrites) for dotnet clean support.

Source and attribution

Source:dotnet/skillsinplugins/dotnet-msbuild/skills/item-managementat commit0608d89

License: MIT

Content belongs to its original authors. SourceWeft indexes it from a public repository.

Report or request removal

Item Management

MSBuild Item Management Patterns

Include / Remove / Update — Three Operations

Include — Add Items

Remove — Subtract Items

Update — Modify Existing Items

Item Batching — %(Metadata)

Target-level batching (Outputs)

Task-level batching

Per-item filtering with Condition

Batching rules

Item Transforms — @(Item->'expression')

Exclude Pattern — Set Subtraction on Include

Conditional Item Inclusion

PrivateAssets on Tool/Analyzer Packages

Common Pitfalls

Cross-product batching

Generated files in source tree

Missing FileWrites

Source and attribution

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