What is a polyfill-first approach in .NET?

It is a strategy that prioritizes using source-generated stubs and implementations to enable modern C# features on older frameworks, reducing the need for messy conditional compilation (#if) blocks.

Does PolySharp add runtime dependencies to my project?

No, PolySharp is a source generator that synthesizes required attributes and types at compile time, meaning it adds zero overhead to your final distributed binary.

How does this skill interact with version detection?

This skill consumes the structured output from dotnet-version-detection to understand the current TFM and C# version, then provides the appropriate targeting and backporting guidance based on that context.

When should I use conditional compilation instead of a polyfill?

Use conditional compilation (#if) when there is a runtime behavior difference that cannot be stubbed, or when you need to utilize a performance-optimized API path available only in newer .NET versions.

.NET Multi-Targeting Strategy

Name: .NET Multi-Targeting Strategy
Author: rudironsoni

byrudironsoni

0•

Developer Tools

Optimizes .NET multi-targeting workflows using polyfill-first strategies and conditional compilation patterns to support multiple frameworks.

This skill provides a comprehensive framework for managing .NET projects that target multiple Target Framework Monikers (TFMs). It guides developers through a 'polyfill-first' approach, utilizing source generators like PolySharp and SimonCropp/Polyfill to enable modern C# language features and BCL APIs on older frameworks without adding runtime dependencies. By integrating with version detection logic, the skill helps maintain clean, maintainable codebases while ensuring binary compatibility and performance optimizations across diverse .NET environments.

Key Features

01Source-generated language feature backporting with PolySharp

02BCL API implementation for older TFMs via SimonCropp/Polyfill

030 GitHub stars

04Polyfill vs. conditional compilation decision matrix

05API compatibility validation using ApiCompat and PackageValidation

06TFM-specific .csproj configuration and source file patterns

Use Cases

01Maintaining a NuGet library that must support both .NET Standard 2.0 and modern .NET 8/9/10+

02Optimizing performance-critical paths with TFM-specific hardware acceleration (e.g., SearchValues)

03Modernizing legacy C# applications with modern syntax while maintaining backward compatibility

What are Skills?·How to Install

Install with 🐟 Skill.Fish

npx skillfish add rudironsoni/rulesync-dotnet dotnet-multi-targeting

For use in Claude.ai and ChatGPT

Key Features

01Source-generated language feature backporting with PolySharp

02BCL API implementation for older TFMs via SimonCropp/Polyfill

030 GitHub stars

04Polyfill vs. conditional compilation decision matrix

05API compatibility validation using ApiCompat and PackageValidation

06TFM-specific .csproj configuration and source file patterns

Use Cases

01Maintaining a NuGet library that must support both .NET Standard 2.0 and modern .NET 8/9/10+

02Optimizing performance-critical paths with TFM-specific hardware acceleration (e.g., SearchValues)

03Modernizing legacy C# applications with modern syntax while maintaining backward compatibility

What are Skills?·How to Install

Install with 🐟 Skill.Fish

npx skillfish add rudironsoni/rulesync-dotnet dotnet-multi-targeting

For use in Claude.ai and ChatGPT