dotsider 0.3.1

dotsider

A TUI for analyzing .NET assemblies — structure, metadata, IL, strings, dependencies, and more. Inspired by binsider for ELF binaries, built for the .NET ecosystem.

dotsider HelloWorld.dll

Installation

dotnet tool (recommended)

dotnet tool install -g dotsider

Homebrew (macOS / Linux)

brew install willibrandon/tap/dotsider

WinGet (Windows)

winget install willibrandon.dotsider

Download binary

Grab a standalone binary from Releases.

What it does

dotsider opens any .NET DLL or EXE and lets you explore it across 8 tabs:

Additional modes

dotsider diff v1.dll v2.dll     # side-by-side assembly comparison
dotsider package.nupkg          # browse NuGet package contents, inspect any DLL inside

Building

Requires .NET 10 SDK.

dotnet build

The binary lands at src/Dotsider/bin/Debug/net10.0/dotsider.

Usage

dotsider <assembly.dll|.exe>    # analyze a .NET assembly
dotsider diff <left> <right>    # compare two assemblies
dotsider <package.nupkg>        # browse a NuGet package

Options:
  -t, --tab <1-8>               start on a specific tab
  -n, --min-len <n>             minimum raw string length (default: 4)
  -v, --version                 show version
  -h, --help                    show help

Keyboard

Hex Dump tab uses vi-style modal editing — the editor starts in normal mode (read-only) to prevent accidental writes:

In insert mode, type two hex digits (0-9, a-f) to overwrite one byte. The first digit sets the high nibble; the second commits the edit. Saving validates the PE image before writing — invalid edits are rejected.

Diff mode adds f to cycle filters (All / Added / Removed / Changed).

How it works

dotsider reads assemblies using APIs that ship with the .NET runtime itself — no third-party analysis libraries needed:

• System.Reflection.Metadata provides MetadataReader for traversing the metadata tables (types, methods, references, custom attributes, string heaps)
• System.Reflection.PortableExecutable provides PEReader for the PE structure (COFF header, sections, CLR header, method bodies)
• System.IO.Compression handles NuGet packages (which are just ZIP files containing a .nuspec manifest and DLLs)

The dynamic analysis tab uses Microsoft.Diagnostics.NETCore.Client to connect to a running .NET process via EventPipe — the same diagnostic infrastructure that powers dotnet-trace and dotnet-counters. It launches your assembly with a reverse-connect diagnostic port, so events are captured from the very first instruction.

The TUI is built on Hex1b, a .NET terminal UI library with a React-inspired declarative API, constraint-based layout, theming, and efficient widget reconciliation.

Project structure

src/Dotsider/
  Analysis/           PE reading, metadata extraction, IL disassembly,
                      diffing, dependency graphs, size analysis, runtime tracing
  Views/              One file per tab — widget trees built each frame
  DotsiderApp.cs      Main app shell (tab panel, key bindings, hints bar)
  DotsiderState.cs    All mutable UI state in one place
  DiffApp.cs          Diff mode shell
  NuGetApp.cs         NuGet mode shell
  Program.cs          CLI entry point and mode routing

samples/
  HelloWorld/         Minimal console app
  ComplexApp/         Async pipeline with embedded resources
  RichLibrary/        Library with NuGet deps (Newtonsoft.Json, System.Text.Json)
  RichLibraryV2/      Same library with deliberate API changes (for diff testing)
  MinimalApi/         ASP.NET Core minimal API (web SDK, hosted entry point)
  NativeLib/          Unsafe code, P/Invoke, pointer operations
  EmptyLib/           Minimal library (edge case testing)

tests/Dotsider.Tests/
  SampleAssemblyFixture.cs   Builds all 7 samples once, shared across tests
  *Tests.cs                  Integration tests against real assemblies

Testing

dotnet test

Integration tests run against real .NET assemblies. The test fixture builds all sample projects automatically. First run takes longer due to NuGet restore; subsequent runs use cache.

Samples

Build the sample assemblies to have something to analyze:

dotnet build samples/RichLibrary
dotsider samples/RichLibrary/bin/Debug/net10.0/RichLibrary.dll

Try diff mode with the two library versions:

dotnet build samples/RichLibraryV2
dotsider diff \
  samples/RichLibrary/bin/Debug/net10.0/RichLibrary.dll \
  samples/RichLibraryV2/bin/Debug/net10.0/RichLibrary.dll

License

MIT