DP44/enriched-qwen3-coder-next/Common/DTS.Common/Events/Diagnostics.md

source_files, generated_at, model, schema_version, sha256

source_files	generated_at	model	schema_version	sha256
Common/DTS.Common/Events/Diagnostics/CheckDataToDownloadEvent.cs	2026-04-16T03:24:51.174525+00:00	Qwen/Qwen3-Coder-Next-FP8	1	99f81a50a8d987c0

Diagnostics

1. Purpose

This module defines a Prism-based event (CheckDataToDownloadEvent) used to signal and coordinate a check for data that needs to be downloaded in the DTS system. It enables decoupled communication between components—typically a producer (e.g., a service or view model) initiating a download readiness check—and subscribers (e.g., a download manager or UI component) responsible for evaluating and acting on whether a download is necessary. The event supports bypassing the check (e.g., for forced or manual downloads) via the BypassCheck flag, and carries a reference to the originating producer for context or audit purposes.

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2. Public Interface

• CheckDataToDownloadEvent

  • Type: class inheriting from PubSubEvent<CheckDataToDownloadEventArgs>
  • Behavior: A Prism PubSubEvent used to publish and subscribe to download-check requests. Subscribers receive an instance of CheckDataToDownloadEventArgs when the event is published.

• CheckDataToDownloadEventArgs

  • Type: class
  • Properties:
    • bool BypassCheck { get; } — Indicates whether the caller requests skipping the normal data existence/validity check (e.g., proceed directly to download).
    • object Producer { get; } — The object that triggered the event (e.g., a view model, service, or UI element). Used for identification or logging.
  • Constructor:
    • CheckDataToDownloadEventArgs(bool bypassCheck, object o) — Initializes the args with the bypass flag and producer reference. Both values are immutable after construction.

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3. Invariants

• BypassCheck is set at construction and never modified afterward (due to private set).
• Producer is set at construction and never modified afterward (due to private set).
• The Producer reference may be null (no validation is performed in the constructor), so consumers must handle null cases.
• The event is strictly for initiating a check—not for reporting results. The event itself does not carry download status or payload; subscribers are expected to handle side effects (e.g., triggering downloads) based on their own logic.

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4. Dependencies

• Depends on:
  • Prism.Events (specifically PubSubEvent<T> from the Prism library).
• Used by:
  • Any component needing to request a data-downloads check (e.g., DownloadService, MainViewModel, or UI controls).
  • Subscribers (e.g., DownloadManager) that react to this event to determine whether to proceed with downloading data.
• No other internal dependencies are evident from this file alone.

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5. Gotchas

• No validation on Producer: The constructor accepts any object, including null. Consumers must defensively check Producer before use (e.g., for logging or routing).
• Event semantics are ambiguous: The name CheckDataToDownloadEvent implies a request, but the event does not provide a way to return a result (e.g., whether download is needed). Subscribers must act asynchronously or via side effects (e.g., publishing a follow-up event).
• No cancellation support: There is no mechanism for subscribers to cancel or delay the check (e.g., via a token).
• No versioning or schema evolution: If BypassCheck or Producer semantics change in the future, this event type offers no backward/forward compatibility.
• None identified from source alone.