Introduction to G#

G# is a modern, simple, and accessible programming language for the .NET runtime. It draws on the everyday ergonomics of Go, Kotlin, and Swift — small surface, explicit types, sealed hierarchies, nullable handling that the binder helps you with — and compiles down to ordinary managed assemblies that any .NET tool can consume.

If you already know .NET, G# gives you another way to build managed assemblies and call CLR APIs — classes, interfaces, properties, events, delegates, exceptions, async workflows, and so on — under the normal dotnet toolchain. If you are coming from Go, Kotlin, Swift, or TypeScript, much of the syntax will already feel familiar.

How G# runs

G# currently has two execution paths:

• The production compiler, gsc, parses, binds, lowers, and emits managed PE assemblies directly. SDK projects use this path through MSBuild, so dotnet build and dotnet run work for .gsproj projects.
• The interpreter path executes the same parsed and bound program in-process. gsc uses this compatibility mode when you pass source files but do not pass /out. It is useful for quick experiments, but some CLR interop features are emit-only. In particular, the interpreter cannot marshal G# function literals into CLR delegates in every place the emitted assembly can.

The default emitted target framework is net10.0; the compiler also recognizes net8.0 and net9.0 target framework mappings.

Who G# is for

G# is for people who want a small, predictable language with direct access to the .NET ecosystem. It is especially useful if you want to learn or teach .NET without starting from C#, or if you prefer a modern, Kotlin-/Swift-shaped syntax but still need CLR interop, MSBuild projects, Portable PDBs, and the broader .NET ecosystem.

The language is still growing. The documentation highlights what works today and calls out differences between the compiler and interpreter where they matter.

The 0.3 line fills in more of the CLR-facing surface: collection initializers, index/range ergonomics, expression-bodied members, partial and nested types, static imports, user indexers and conversion operators, unsafe pointers, stackalloc, fixed, unmanaged / sizeof, and Kotlin-style object { ... } anonymous objects.

Where to start

• Install G# to set up the SDK, templates, or a source-built compiler.
• Quickstart: Hello, G# to compile and run your first program.
• A Tour of G# for a short guided walk through syntax, types, control flow, concurrency, and .NET interop.
• Tutorials for task-oriented walkthroughs.
• Language specification when you need the reference details.