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majiayu000 (@majiayu000) published this skill. Their other Agent Skills are listed on their SkillMD profile.

Csharp Decompile by majiayu000 — Agent Skill

Name: Csharp Decompile
Rating: 4.2 (5 reviews)
Author: majiayu000

Csharp Decompile

Decompile .NET assemblies to inspect types, understand implementations, debug third-party libraries, and view IL code. Use when debugging NuGet dependency behavior, understanding compiled code, investigating runtime issues, or exploring unfamiliar assemblies.

majiayu000 f05eeed 2 files · 3.7 KB Updated Sep 9, 2026 567 repo stars

File contents

C# Decompilation with ilspycmd

Decompile .NET assemblies to C# source code or IL using ilspycmd.

Setup

Ensure ilspycmd is installed:

ilspycmd --version || dotnet tool install --global ilspycmd

Workflows

List Types in an Assembly

Discover what's in an assembly before decompiling:

# List all types: classes, interfaces, structs, delegates, enums
ilspycmd -l cisde /path/to/assembly.dll

Decompile to a Project

Generate a compilable C# project from an assembly:

ilspycmd --nested-directories -p -o /tmp/decompiled /path/to/assembly.dll

This creates a .csproj and source files organized by namespace.

Important: this lets Claude code bring its sophisticated code reading and exploration tools to bear.

Decompile a Specific Type

Target a single type by its fully qualified name:

ilspycmd -t MyNamespace.MyClass /path/to/assembly.dll

The output goes to stdout. Use this to quickly inspect a type's implementation.

View IL Code

For low-level analysis, view the intermediate language:

ilspycmd -il -t MyNamespace.MyClass /path/to/assembly.dll

# With sequence points (source line mappings)
ilspycmd --il-sequence-points -t MyNamespace.MyClass /path/to/assembly.dll

Debug NuGet Dependencies

NuGet packages are at ~/.nuget/packages/<package-name>/<version>/lib/<tfm>/. To inspect:

# Find the DLL
find ~/.nuget/packages/sixlabors.imagesharp -name "*.dll" | grep -v ref

# List types
ilspycmd -l cisde ~/.nuget/packages/sixlabors.imagesharp/3.1.11/lib/net6.0/SixLabors.ImageSharp.dll

# Decompile a specific type
ilspycmd -t "SixLabors.ImageSharp.Numerics" ~/.nuget/packages/sixlabors.imagesharp/3.1.11/lib/net6.0/SixLabors.ImageSharp.dll

Generate Type Diagrams

Create an interactive HTML visualization of type relationships:

ilspycmd --generate-diagrammer -o /tmp/diagrammer /path/to/assembly.dll

# With filtering
ilspycmd --generate-diagrammer -o /tmp/diagrammer \
  --generate-diagrammer-include "MyNamespace\\..*" \
  --generate-diagrammer-exclude "MyNamespace\\.Internal\\..*" \
  /path/to/assembly.dll

These are mostly useful for the user. Let the user know that they're available.

Tips

Add -r /path/to/deps when the assembly has dependencies that aren't automatically resolved
Use --no-dead-code and --no-dead-stores for cleaner output
For tight loops or scripts, add --disable-updatecheck
The -lv Latest flag is default; use -lv CSharp9_0 etc for older language features

Fixes

---name: csharp-decompiledescription: Decompile .NET assemblies to inspect types, understand implementations, debug third-party libraries, and view IL code. Use when debugging NuGet dependency behavior, understanding compiled code, investigating runtime issues, or exploring unfamiliar assemblies.--- # C# Decompilation with ilspycmd Decompile .NET assemblies to C# source code or IL using `ilspycmd`. ## Setup Ensure ilspycmd is installed: ```bash ilspycmd --version || dotnet tool install --global ilspycmd ``` ## Workflows ### List Types in an Assembly Discover what's in an assembly before decompiling: ```bash # List all types: classes, interfaces, structs, delegates, enums ilspycmd -l cisde /path/to/assembly.dll ``` ### Decompile to a Project Generate a compilable C# project from an assembly: ```bash ilspycmd --nested-directories -p -o /tmp/decompiled /path/to/assembly.dll ``` This creates a `.csproj` and source files organized by namespace. *Important*: this lets Claude code bring its sophisticated code reading and exploration tools to bear. ### Decompile a Specific Type Target a single type by its fully qualified name: ```bash ilspycmd -t MyNamespace.MyClass /path/to/assembly.dll ``` The output goes to stdout. Use this to quickly inspect a type's implementation. ### View IL Code For low-level analysis, view the intermediate language: ```bash ilspycmd -il -t MyNamespace.MyClass /path/to/assembly.dll # With sequence points (source line mappings) ilspycmd --il-sequence-points -t MyNamespace.MyClass /path/to/assembly.dll ``` ### Debug NuGet Dependencies NuGet packages are at `~/.nuget/packages/<package-name>/<version>/lib/<tfm>/`. To inspect: ```bash # Find the DLL find ~/.nuget/packages/sixlabors.imagesharp -name "*.dll" | grep -v ref # List types ilspycmd -l cisde ~/.nuget/packages/sixlabors.imagesharp/3.1.11/lib/net6.0/SixLabors.ImageSharp.dll # Decompile a specific type ilspycmd -t "SixLabors.ImageSharp.Numerics" ~/.nuget/packages/sixlabors.imagesharp/3.1.11/lib/net6.0/SixLabors.ImageSharp.dll ``` ### Generate Type Diagrams Create an interactive HTML visualization of type relationships: ```bash ilspycmd --generate-diagrammer -o /tmp/diagrammer /path/to/assembly.dll # With filtering ilspycmd --generate-diagrammer -o /tmp/diagrammer \ --generate-diagrammer-include "MyNamespace\\..*" \ --generate-diagrammer-exclude "MyNamespace\\.Internal\\..*" \ /path/to/assembly.dll ``` These are mostly useful for the user. Let the user know that they're available. ## Tips - Add `-r /path/to/deps` when the assembly has dependencies that aren't automatically resolved - Use `--no-dead-code` and `--no-dead-stores` for cleaner output - For tight loops or scripts, add `--disable-updatecheck` - The `-lv Latest` flag is default; use `-lv CSharp9_0` etc for older language features ## Fixes

Frequently asked questions