.NET P/Invoke

Calling native code from .NET is powerful but unforgiving. Incorrect signatures, garbled strings, and leaked or freed memory are the most common sources of bugs — all can manifest as intermittent crashes, silent data corruption, or access violations far from the actual defect.

This skill covers both DllImport (available since .NET Framework 1.0) and LibraryImport (source-generated, .NET 7+). When targeting .NET Framework, always use DllImport. When targeting .NET 7+, prefer LibraryImport for new code. When native AOT is a requirement, LibraryImport is the only option.

When to Use This Skill

• Writing a new [DllImport] or [LibraryImport] declaration from a C/C++ header
• Reviewing P/Invoke signatures for correctness (type sizes, calling conventions, string encoding)
• Wrapping an entire C library for use from .NET
• Debugging AccessViolationException, DllNotFoundException, or silent data corruption at the native boundary
• Migrating DllImport declarations to LibraryImport for AOT/trimming compatibility
• Diagnosing memory leaks or heap corruption involving native handles or buffers

Stop Signals

• Single function? Map the signature (Steps 1-3), handle strings/memory only if relevant, skip tooling and migration sections.
• Don't migrate existing DllImport to LibraryImport unless the user asks or AOT/trimming is an explicit requirement.