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MSBuild Extension Points · dotnet | DecimalAI

codingby dotnet

MSBuild Extension Points

dotnet/extension-points

Source dotnet/skills ↗License MIT

Guide for MSBuild extensibility: CustomBefore/CustomAfter hooks, wildcard imports with alphabetic ordering, import gating with control properties, NuGet package build extension layout (build/buildTransitive), and the MicrosoftCommonPropsHasBeenImported guard. USE FOR: diagnosing and fixing MSBuild import and hook patterns, reviewing and fixing extension point anti-patterns in Directory.Build files, fixing missing Exists() guards on imports that break fresh clones, fixing NuGet package hooks bein

SkillScore100Maintained

Automatic

Coding pack

Last verified 8/10/2026

What it changes

Passed 22 of 22 test cases with the skill, and 20 of 22 without it.

Without skill91%

With skill100%

Checks it passed that the model alone missed

The response does not add an Exists condition to the package import tag.
The response uses GetFileName and GetDirectoryName on MSBuildThisFileDirectory to derive the TFM folder name rather than using TargetFramework.
The response states that nuspec file checks should be restricted to the project directory and its immediate parent directory without searching further up.

and 1 more in the full report

2 fixed20 passed either way0 still failing0 broke

Pass-rate lift: +9 pp
Tokens: +95%
Agent turns: 0%
Response time: -41%

Model gemini-3.6-flashMeasured 8/10/2026v122 of 22 cases passed with skill

Tokens, turns and time describe resource use, not a dollar price.

Use this skill

Save it into your project's skills folder. Claude Code picks it up in its next session.

curl -fsSL --create-dirs -o .claude/skills/dotnet-extension-points/SKILL.md https://app.decimal.ai/s/dotnet-extension-points/SKILL.md

Want it pinned and updatable? pip install "decimalai>=0.15", then decimalai skills add dotnet-extension-points, and start Claude Code with claude --plugin-dir "$(git rev-parse --show-toplevel)/.agents"

1 · One-time — install the CLI (docs ↗)

pip install "decimalai>=0.15"

2 · Get the skill — writes .agents/skills/dotnet-extension-points/ and pins it in .decimal/skills.lock

decimalai skills add dotnet-extension-points

No CLI? Get the same file — curl · raw file

curl -fsSL --create-dirs -o .claude/skills/dotnet-extension-points/SKILL.md https://app.decimal.ai/s/dotnet-extension-points/SKILL.md

Raw file: /s/dotnet-extension-points/SKILL.md ↗ · machine-readable summary at /s/dotnet-extension-points.json ↗

Safety checks: 3 of 3 passed

Code scan CleanIntent PassedContent Clean

See it in action

One of 2 test cases the skill fixed. Same model, same prompt, with and without the skill.

1 of 2

Prompt

I am packaging a multi-targeted NuGet tool called DataSync.Engine with props and targets in both build/ and buildTransitive/ folders per TFM. How should I structure the import logic inside buildTransitive/<tfm>/DataSync.Engine.props so it safely delegates to the corresponding file in build/ across transitive projects without breaking during restore or target evaluation? Please provide the exact MSBuild XML snippet for the transitive props file and explain the path resolution pattern.

What was checked, without and with the skill
Checked	Without skill	With skill
The response uses GetFileName and GetDirectoryName on MSBuildThisFileDirectory to derive the TFM folder name rather than using TargetFramework.	Missed	Passed
The response does not add an Exists condition to the package import tag.	Missed	Passed

case-01 · gemini-3.6-flash · 8/10/2026 · answers are capped and redacted

What's inside

The instructions your model reads when the skill loads.

SKILL.md238 linessingle file

MSBuild Extension Points

How the MSBuild pipeline provides hooks for SDKs, NuGet packages, repos, and users to inject custom logic.

CustomBefore / CustomAfter Hooks

Every major .targets file defines import hooks:

<PropertyGroup>
  <CustomBeforeMicrosoftCommonTargets Condition="'$(CustomBeforeMicrosoftCommonTargets)' == ''">
    $(MSBuildExtensionsPath)\v$(MSBuildToolsVersion)\Custom.Before.Microsoft.Common.targets
  </CustomBeforeMicrosoftCommonTargets>
</PropertyGroup>

<Import Project="$(CustomBeforeMicrosoftCommonTargets)"
    Condition="'$(CustomBeforeMicrosoftCommonTargets)' != '' and Exists('$(CustomBeforeMicrosoftCommonTargets)')"/>
<!-- ... core targets ... -->
<Import Project="$(CustomAfterMicrosoftCommonTargets)"
    Condition="'$(CustomAfterMicrosoftCommonTargets)' != '' and Exists('$(CustomAfterMicrosoftCommonTargets)')"/>

Rules

Default path includes version (v$(MSBuildToolsVersion)) for side-by-side installations.
Always check Exists(). The file may not be present on every machine.
Append to the property (don't overwrite) to chain multiple hooks:

<PropertyGroup>
  <CustomBeforeMicrosoftCommonTargets>
    $(CustomBeforeMicrosoftCommonTargets);$(MSBuildThisFileDirectory)MyExtension.targets
  </CustomBeforeMicrosoftCommonTargets>
</PropertyGroup>

Wildcard Import Directories

MSBuild imports all files in extension directories, sorted alphabetically:

Track record

Benchmark

22 / 22

test cases passed, vs 20 / 22 without

Adoption

Users: 0
Times used: 0

Safety and source details

SkillSafety

✓ 3 of 3 passed

Code scan15 of 15 checks clean

0 critical · 0 warning · 0 info — scanner v4 — 8/3/2026

View 15 scanner checks

live_secretremote_code_executionreverse_shelldata_exfiltrationssrf_metadataagent_snoopinganti_refusaldestructive_commandsobfuscated_unicodeunicode_homoglyphopaque_blobsuspicious_urltool_overreachtrigger_abuseprompt_injection_phrasing

IntentSafe

LLM judge · does the skill do what it claims

ContentClean

LLM judge · policy & harmful-content review

Source

Imported

dotnet / skills

plugins/dotnet-msbuild/skills/extension-points/SKILL.md

View on GitHub ↗

License MITImported 8/3/2026Version v1

More skills from the same source and nearby in the registry, with their headline benchmark lift.

Ready to supercharge your AI agents?

See it in action

What's inside

MSBuild Extension Points

CustomBefore / CustomAfter Hooks

Rules

Wildcard Import Directories

Track record

Benchmark

Adoption

SkillSafety

Source

Related skills