dotnet-multi-targeting

Comprehensive guide for .NET multi-targeting strategies with a polyfill-first approach. This skill consumes the structured output from [skill:dotnet-version-detection] (TFM, C# version, preview flags) and provides actionable guidance on backporting language features, handling runtime gaps, and validating API compatibility across target frameworks.

Out of scope: TFM detection logic (owned by [skill:dotnet-version-detection]), version upgrade lane selection (see [skill:dotnet-version-upgrade]), platform-specific UI frameworks (MAUI, Blazor), cloud deployment configuration.

Cross-references: [skill:dotnet-version-detection] for TFM resolution and version matrix, [skill:dotnet-version-upgrade] for upgrade lane guidance and migration strategies.

Decision Matrix: Polyfill vs Conditional Compilation

Use this matrix to select the correct strategy for each type of gap between your highest and lowest TFMs.