ilspy-decompile_skill

Overview

This skill helps you inspect compiled .NET binaries by decompiling assemblies with ILSpy. It lets you read C# or IL output, explore types and members, and extract project-like source for analysis or debugging. Use it to learn implementation details, audit third-party packages, or recover lost source for investigation.

How this skill works

The skill runs the ILSpy command-line tool (ilspycmd or dnx ilspycmd) against target DLLs or EXEs. It can print decompiled code to stdout, write a decompiled project folder, or target specific types, languages, or IL output. The workflow is: locate the assembly, list available types, and run targeted or full decompilation with appropriate flags.

When to use it

• You want to inspect how a NuGet package implements an API without source access.
• You need to debug or understand behavior in a compiled dependency.
• You want to review framework or runtime implementations shipped in .NET runtimes.
• You need to recover logic from a compiled build when source is missing.
• You’re auditing compiled binaries for security or licensing concerns.

Best practices

• Prefer non-trimmed, non-AOT builds for more readable decompiled output.
• Verify the ilspycmd version and supported flags with ilspycmd -h before use.
• Use -o to export a project folder when you want to navigate multiple types.
• Target specific types with -t to reduce noise and speed up inspection.
• Be mindful of license and legal restrictions before decompiling third-party assemblies.

Example use cases

• Decompile a NuGet package assembly from ~/.nuget/packages to inspect an internal helper method.
• Run ilspycmd -o ./decompiled MyLibrary.dll to get a browsable project for code review.
• Use ilspycmd -il MyRuntimeLib.dll to view the IL when investigating performance or JIT behavior.
• Target a class with ilspycmd -t Namespace.ClassName to focus on a single implementation detail.