Add simple parent-child linked cancellation token example

[Copilot]

The "Cancellation in Managed Threads" article lacked a basic example of CreateLinkedTokenSource for the parent-child pattern — the most common reason developers reach for linked tokens.

Changes

• New snippets (docs/standard/threading/snippets/cancellation-in-managed-threads/{csharp,vb}/LinkedTokens/): self-contained C# and VB console projects demonstrating the minimal parent-child pattern
• Article update (cancellation-in-managed-threads.md): restructured "Listening to multiple tokens simultaneously" to lead with the simple example before the existing complex class-based scenario; updated ms.date and added ai-usage: ai-assisted

using var parentCts = new CancellationTokenSource();
using var childCts = CancellationTokenSource.CreateLinkedTokenSource(parentCts.Token);

parentCts.Cancel();

Console.WriteLine(parentCts.Token.IsCancellationRequested); // True
Console.WriteLine(childCts.Token.IsCancellationRequested);  // True

Original prompt

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This section details on the original issue you should resolve

<issue_title>Missing simple example how to create parent-child tokens</issue_title>
<issue_description>
[Enter feedback here]

Something like the following, which must be the most common use case for linking.

https://stackoverflow.com/questions/29623178/linking-cancellation-tokens

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Document Details

⚠ Do not edit this section. It is required for docs.microsoft.com ➟ GitHub issue linking.

• ID: 51f5ff8f-7d37-af59-4b51-41de21d67b95
• Version Independent ID: ef30d618-f141-3943-b93b-ce697ca8991b
• Content: Cancellation in Managed Threads
• Content Source: docs/standard/threading/cancellation-in-managed-threads.md
• Product: dotnet
• Technology: dotnet-standard
• GitHub Login: @BillWagner
• Microsoft Alias: wiwagn</issue_description>

Comments on the Issue (you are @copilot in this section)

@tdykstra Thanks for the suggestion - we'll add an example the next time the article is updated.

• Fixes Missing simple example how to create parent-child tokens #21360

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Internal previews

📄 File	🔗 Preview link
docs/standard/threading/cancellation-in-managed-threads.md	docs/standard/threading/cancellation-in-managed-threads

[BillWagner]

This is ready for final review.

[Copilot]

Pull request overview

This PR updates the Cancellation in Managed Threads documentation to include a minimal parent-child linked cancellation token example using CancellationTokenSource.CreateLinkedTokenSource, supported by new self-contained C# and Visual Basic snippet projects.

Changes:

• Added new C# and VB console snippet projects demonstrating a simple parent→child linked token pattern.
• Restructured the “Listening to multiple tokens simultaneously” section to lead with the new simple example before the existing more complex scenario.
• Updated article frontmatter (ms.date, and ai-usage).

Reviewed changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
docs/standard/threading/snippets/cancellation-in-managed-threads/csharp/LinkedTokens/Program.cs	Adds the minimal C# linked-token example used by the article.
docs/standard/threading/snippets/cancellation-in-managed-threads/csharp/LinkedTokens/LinkedTokens.csproj	Adds a self-contained C# console project to build/run the snippet.
docs/standard/threading/snippets/cancellation-in-managed-threads/vb/LinkedTokens/Program.vb	Adds the minimal VB linked-token example used by the article.
docs/standard/threading/snippets/cancellation-in-managed-threads/vb/LinkedTokens/LinkedTokens.vbproj	Adds a self-contained VB console project to build/run the snippet.
docs/standard/threading/cancellation-in-managed-threads.md	Reorders and expands the linked-token section, and embeds the new snippets.