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Async/await UdonSharp example

Documentation version: 0.3.5 · All examples · Package guide

This folder contains real U# examples for the build-time async lowering:

  • AsyncYieldDelayExample uses Task.Yield() and Task.Delay(int);
  • AsyncStringDownloadExample awaits VRCAsync.LoadStringAsync(url, out result) while keeping the traditional OnStringLoadSuccess/OnStringLoadError callbacks;
  • AsyncImageDownloadExample awaits VRCAsync.LoadImageAsync while keeping the traditional image callbacks;
  • AsyncVideoLoadExample and AsyncVideoEndExample cover video readiness, errors, and playback completion;
  • AsyncGpuReadbackExample covers VRCAsyncGPUReadback;
  • AsyncSerializationExample keeps both serialization callbacks;
  • AsyncAvailableProductsExample, AsyncPurchasesExample, and AsyncProductOwnersExample cover Creator Economy list operations.

Add an example to a GameObject with its paired UdonSharpProgramAsset (the .asset next to each .cs, same basename), assign its URL and (for images) target material, enter the world, and interact with it.

Currently supported in this slice:

  • parameterless, instance, non-generic, non-network-callable async void methods;
  • straight-line await Task.Yield(); statements;
  • straight-line await Task.Delay(milliseconds); statements where milliseconds is a positive compile-time constant;
  • one VRChat SDK await per behaviour, including string/image downloads, video, GPU readback, manual serialization, and Creator Economy list operations.

For SDK awaits, the traditional callback body runs first and receives the SDK result. For the string downloader's out overload, the compiler then copies that SDK result into the supplied instance behaviour field before running the generated await continuation. The original LoadStringAsync(url) overload remains available. Array elements and async locals are rejected until their storage locations can be safely hoisted. Assigning a Task<T> result directly to an async local is not supported yet.

Do not start another string request with the same URL on the behaviour while its await is pending. String completion is correlated by URL; image completion is correlated by the returned IVRCImageDownload request identity. Each async method is single-flight: another call while its continuation is pending is ignored.

Video callbacks do not identify their source player, so do not start a manual video operation on the same behaviour while a video await is pending. Keep the video player and awaiting behaviour on the same GameObject. Economy list operations have no SDK error callback and can therefore remain pending.

Locals, parameters, nested awaits, explicit returns, direct Task<T> result assignment and multiple simultaneous SDK awaits still produce build diagnostics until their later frame-pool lowering slices are implemented.