| name | ilspy-decompile |
| description | 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. Use when this capability is needed. |
| metadata | {"author":"aaronontheweb"} |
.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:
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
ilspycmd MyLibrary.dll
dnx ilspycmd MyLibrary.dll
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
- Decompile the target
Commands
Basic decompilation
ilspycmd MyLibrary.dll
ilspycmd -o ./decompiled MyLibrary.dll
ilspycmd -p -o ./project MyLibrary.dll
Targeted decompilation
ilspycmd -t Namespace.ClassName MyLibrary.dll
ilspycmd -lv CSharp12_0 MyLibrary.dll
View IL code
ilspycmd -il MyLibrary.dll
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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