ReddRadar
Agent skill
ilspy-decompile
Understand implementation details of .NET code by decompiling assemblies. Use when you want to see how a .NET API works internally, inspect NuGet package source, view framework implementation, or understand compiled .NET binaries.
Install this agent skill to your Project
npx add-skill https://github.com/NikiforovAll/claude-code-rules/tree/main/plugins/handbook-dotnet/skills/ilspy-decompile
SKILL.md
.NET Assembly Decompilation with ILSpy
Use this skill to understand how .NET code works internally by decompiling compiled assemblies.
Prerequisites
- .NET SDK installed
- ILSpy command-line tool available via one of the following:
dotnet dnx ilspycmd(if available in your SDK or runtime)dotnet tool install --global ilspycmd
Both forms are shown below. Use the one that works in your environment.
Note: ILSpyCmd options may vary slightly by version. Always verify supported flags with
ilspycmd -h.
Quick start
# Decompile an assembly to stdout
ilspycmd MyLibrary.dll
# or
dotnet dnx ilspycmd MyLibrary.dll
# Decompile to an output folder
ilspycmd -o output-folder MyLibrary.dll
Common .NET Assembly Locations
NuGet packages
~/.nuget/packages/<package-name>/<version>/lib/<tfm>/
.NET runtime libraries
dotnet --list-runtimes
.NET SDK reference assemblies
dotnet --list-sdks
Reference assemblies do not contain implementations.
Project build output
./bin/Debug/net8.0/<AssemblyName>.dll
./bin/Release/net8.0/publish/<AssemblyName>.dll
Core workflow
- Identify what you want to understand
- Locate the assembly
- List types to find the target
- Decompile the target
Commands
List types in an assembly
Use -l with an entity type to discover what's inside:
# List classes
ilspycmd -l c MyLibrary.dll
# List interfaces
ilspycmd -l i MyLibrary.dll
# List structs, delegates, enums
ilspycmd -l s MyLibrary.dll
ilspycmd -l d MyLibrary.dll
ilspycmd -l e MyLibrary.dll
Basic decompilation
ilspycmd MyLibrary.dll
ilspycmd -o ./decompiled MyLibrary.dll
ilspycmd -p -o ./project MyLibrary.dll
Targeted decompilation
# Decompile specific type
ilspycmd -t Namespace.ClassName MyLibrary.dll
# Specify C# language version (default: Latest)
ilspycmd -lv CSharp12_0 MyLibrary.dll
View IL code
ilspycmd -il MyLibrary.dll
Clean output
# Remove dead code and dead stores for cleaner results
ilspycmd --no-dead-code --no-dead-stores MyLibrary.dll
Organized project output
# Decompile with nested directories matching namespaces
ilspycmd --nested-directories -p -o ./decompiled MyLibrary.dll
References
- references/diagrammer.md — Generate interactive HTML diagrams from assemblies. Load when the user asks to visualize or explore type relationships.
Notes on modern .NET builds
- ReadyToRun images may reduce readability
- Trimmed or AOT builds may omit code
- Prefer non-trimmed builds
Legal note
Decompiling assemblies may be subject to license restrictions.
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