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C# Async Profile

Standards metadata

  • ID: profile.language.csharp.async
  • Role: profile
  • Level: PROFILE
  • Applies when: C# asynchronous code crosses an await boundary whose continuation scheduling, synchronization context, thread affinity, cancellation, or lifetime affects correctness.
  • Does not apply when: No C# async mechanism changes or the operation is proven synchronous and immediate.
  • Requires: core, workflow.verification, topic.concurrency
  • Specializes: topic.concurrency
  • Verification: C# continuation-affinity and lifecycle decisions plus focused runtime tests for every selected scheduling mechanism.
  • Canonical owner: profiles/languages/csharp/async.md

Inherit The Generic Lifecycle Contract

Concurrency And Async Lifecycle owns work, failure, cancellation, nonblocking execution, and shutdown. This profile owns only C# continuation-scheduling mechanisms and evidence.

An await, Task, synchronization context, scheduler, or dispatcher does not change the generic owner or permit detached work, discarded failure, ignored cancellation, blocking waits, or state from a prior invocation.

Select Continuation Scheduling From Affinity

Establish whether the continuation requires a specific synchronization context, scheduler, thread, or dispatcher before selecting a mechanism.

Use context suppression such as ConfigureAwait(false) only when the selected API supports it and the continuation contract proves that captured context is not required. Preserve or explicitly dispatch to the required context when continuation work has UI, engine, actor, or other thread-affinity obligations.

Library, service, handler, or application location alone does not prove either decision. Do not apply context suppression globally, depend on implicit capture, or add an alternate dispatcher as fallback.

Preserve Invocation Isolation

Each invocation supplies its own inputs, cancellation, result destination, and terminal outcome. A long-lived service or reused runtime may retain declared shared resources, but it must not carry request inputs, synchronization context, cancellation state, or result ownership from an earlier invocation.

Typed Outcomes

Return the operation's typed invalid, unsupported, or unavailable diagnostic when affinity requirements contradict the selected mechanism, the API cannot provide the required scheduling behavior, or required affinity and evidence are unknown. Preserve a more specific operation failure when one exists.

Do not continue with context suppression, implicit capture, synchronous blocking, detached work, alternate dispatch, or default success.

Verification

Evidence must cover the selected continuation contract, including applicable:

  • context-free continuation with supported context suppression;
  • affinity-required continuation on or dispatched to the required context;
  • failure and cancellation observation across the await boundary;
  • repeated invocations with distinct inputs and cancellation;
  • rejection of contradictory affinity and scheduling choices; and
  • typed failure when required scheduling capability or evidence is absent.