Update documentation for AddHostedService.

[cincuranet]

Fixes #53831.

[Copilot]

Pull request overview

This PR updates the XML documentation for the AddHostedService extension methods to clarify that these methods only register the service as IHostedService in the DI container, not as the concrete type itself. This addresses confusion reported in issue #53831 where developers expected the concrete type to also be registered.

Changes:

• Added <remarks> sections to both overloads of AddHostedService explaining the registration behavior
• Included code examples demonstrating the workaround pattern for registering both the concrete type and the hosted service

[Shane32]

This suggested solution will cause the service to be disposed twice when the service collection is disposed, correct? (assuming it implements IDisposable)

[cincuranet]

That's correct.

But I don't see problem with that. The IDisposable docs clearly states:

If an object's Dispose method is called more than once, the object must ignore all calls after the first one. The object must not throw an exception if its Dispose method is called multiple times.