C# support inventory

This inventory describes the closed families proved by the C# target. Individual .NET APIs remain governed by their reflected declarations and exact provider relations.

TypeScript language families

• ESM modules, source packages, side-effect imports, re-exports, module initialization, and default exports;
• functions, classes, interfaces, enums, aliases, constructors, inheritance, statics, generics, overload implementations, callbacks, and closures;
• primitives, arrays, rectangular arrays, tuples, fixed arrays, records, structural object shapes, nullable values, discriminated unions, and finite broad values;
• arithmetic, comparison, bitwise and boolean operators, updates, assignments, spreads, optional chains, nullish coalescing, assertions, and selected conversions;
• blocks, branches, switch, loops, exceptions, cleanup, async/await, synchronous/asynchronous iteration, generators, and resource management;
• all pinned TypeScript utility types when their resolved callable, tuple, string-literal, union, or object shape has a closed C# representation.

.NET families

• framework and configured assembly namespaces through @tsonic/dotnet/*;
• classes, structs, interfaces, enums, delegates, constructors, methods, properties, fields, indexers, events, inheritance, and attributes;
• generic type/method families, constraints, nullable metadata, optional and default parameters, params, by-reference modes, arrays, pointers, function pointers, and tasks;
• provider-backed object initializers only when exact field/property relations and construction policy exist.

The inventory is metadata-shaped: Tsonic does not maintain a hand-written allowlist of BCL type names.

Check one .NET API

Import the exact namespace and let the selected framework/assembly metadata answer the question:

import { File } from "@tsonic/dotnet/System.IO.js";

export function read(path: string): string {
  return File.ReadAllText(path);
}

If the type, overload, conversion, or assembly relation is unavailable, the build fails at the import or provider boundary. The documentation therefore lists supported metadata families rather than copying the evolving .NET API catalog.

JavaScript families

• arrays, strings, numbers, Math, maps, sets, dates, JSON including replacer callbacks and selected toJSON, RegExp, promises, Intl, symbols, weak collections, console, timers, numeric typed arrays, closed object-shape operations, and explicit JsString UTF-16 behavior;
• exact overloads and operations supplied by the selected JavaScript source profile and C# operation tables;
• no embedded JavaScript engine, open reflection, or best-effort dispatch.

Node families

• path, URL, filesystem, filesystem promises, process, OS, Buffer, HTTP, crypto, zlib, utilities, timers, assertions, and declared stream/sink contracts;
• canonical node:* imports resolved by @tsonic/csharp-nodejs to static C# runtime calls;
• binary buffers and HTTP bodies, process state, timing/memory metrics, and exact filesystem option objects where declared.

Explicit target boundaries

• unproved provider identity, conversion, storage, location, safety, or metadata shape;
• runtime module cycles whose ESM initialization cannot be preserved;
• open object graphs or dynamic calls that require CLR reflection;
• target-specific generator or pointer combinations outside the approved native/runtime protocols.

For exact configuration and rejection rules, see configuration and limitations.