CS2X (Under development)

Transpiles a C# subset to non .NET languages, platforms, runtimes and enviroments. (Powered by Roslyn)

CS2X is activily being tested in the development of the Orbital-Framework:
This provides real-world tests and as things progress more features will tested and supported here.


Renders a 1280x720 image then prints how long it took in seconds.


This project will focus on transpiling a C# subset with a modified type system for writing CPU and GPU programs.

  • Custom Standard lib(s) for various targets.
  • Documentation

CPU targets

  • C89
    • Native C performance
    • C89: modern, legacy and embedded platforms (x86, MIPS, SPARC, RISC-V, PPC, M68K, AVR, etc)
    • CC65: 6502 platforms (Atari, C64, NES, Apple II, etc)
    • SDCC: Many targets (ColecoVision, ZX Spectrum, etc)
    • z88dk: Z80 platforms
  • LLVM
  • LLVM IR => Assembly: CP1610 (Intellivision)
  • LLVM IR => Assembly: Intel 8048 (Magnavox Odyssey 2)
  • LLVM IR => Retarget: Custom assembly targets (FPGA CPU, 16bit bytes, etc)
  • Java
  • Kotlin
  • javaScript
  • Python
  • ActionScript

GPU targets

  • HLSL (DirectX Shader Assembly Language) [D3D9.0c +]
  • ALS (DirectX Shader Assembly Language) [D3D8.0 - D3D9.0c]
  • GLSL (OpenGL shading language) [OpenGL2.0 / GLES2 +]
  • ARB (ARB assembly language) [legacy / homebrew systems]
  • CG (Cg programming language) [PSVita, Nvidia / other]
  • PSSL (PlayStation Shader Language) [PS4]
  • MSL (Metal Shading Language) [macOS / iOS]
  • AGAL (Adobe Graphics Assembly Language)
  • Custom: Plugin system

Primary Project libraries

  • CS2X.Core: .NET transpiler lib
  • CS2X.CLI: CLI interface for CS2X.Core
  • CS2X.Analyzer: C# syntax analyzer to limit unsuported features.
  • CS2X.CoreLib: Portable CoreLib subset

How does it basically work?

  • C89
    • Each executable gets built to a single '.c' source file including all dependencies.
    • String literals on embedded devices, cartridges, etc can be stored in program memory / ROM to save ram.
    • All GC methods are agnostic allowing any built-in or custom GC backend.
  • Other: TODO


Almost zero performance loss. C# code will generate in a manner as if hand written in the target language in many respects. There are a couple key differences in the CS2X runtime / type system vs .NET CLR

  • Structs are not part of the object system as they are in the .NET runtime.
    • No auto boxing for value types are supported (.NET has many easy to fall in syntax performance pitfalls here).
    • System.Object can never equal a 'struct', 'enum' or 'primitive' type.
    • Virtuals like 'MyStruct.GetType()' or 'MyEnum.GetType()' give compile time errors (use typeof instead).
    • Cannot bind a delegate to a structs non-static method.
  • Interfaces are considered 'type-classes' and are compile time only.
    • Used for generics or general code consistency.
    • No casting to them or variable declarations of them.
  • No up-casting performance loss in C and down-casting checks can be disabled for C output.
  • Auto-Marshalling of managed types not supported.
    • Varies to much between platforms in contrast to .NET making writing portable code confusing.
    • Auto string marshalling has way to many implicits that depend on to many factors to keep track of.
    • Redundant allocations. If you want to pass the same string multiple times in multiple methods for example auto-marshaling it everytime doesn't make sense. Its far better to be explicit here and make that obvious by pre-marshalling the type once.
    • Portability. Forcing PInvokes to be used this way ensures code functions the same in all runtimes.


  • Prerequisites
    • Visual Studios 2019 (VS for Mac / MonoDevelop or VSCode have not yet been tested)
    • .NET Core 3.1
    • .NET Compiler Platform SDK
  • Run: CS2X.Core.Test proj in VS. This will build "PortableTestApp.csproj" to "TestOutput" folder
  • NOTE: Early stages so nothing else is supported yet.


Transpiles a C# subset to non .NET languages and runtimes. (Powered by Roslyn)

Cs2x Info

⭐ Stars 85
🔗 Source Code
🕒 Last Update 8 months ago
🕒 Created 3 years ago
🐞 Open Issues 2
➗ Star-Issue Ratio 43
😎 Author reignstudios