Document not clear as to how to avoid duplicate events being handled

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https://docs.microsoft.com/en-us/dotnet/architecture/microservices/multi-container-microservice-net-applications/subscribe-events#deduplicating-message-events-at-the-eventhandler-level

Here the document talks about using the custom RequestId to uniquely mark each event so that it won't be handled more than once. However, it only mentions the event was constructed with the RequestId, without the logic as to checking this property and handling the duplicate based on this check result. The missing mechanism is the key point, as a matter of fact.

On the other hand, the sample eshop solution code doesn't seem to check this RequestId property either.

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#### Document Details

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* ID: 384e5c2c-d3ba-b5ba-260b-65b8e900b78e
* Version Independent ID: 534541bb-0ffe-f7d6-8cc3-22da784c96a6
* Content: [Subscribing to events](https://docs.microsoft.com/en-us/dotnet/architecture/microservices/multi-container-microservice-net-applications/subscribe-events#deduplicating-message-events-at-the-eventhandler-level)
* Content Source: [docs/architecture/microservices/multi-container-microservice-net-applications/subscribe-events.md](https://github.com/dotnet/docs/blob/main/docs/architecture/microservices/multi-container-microservice-net-applications/subscribe-events.md)
* Product: **dotnet-architecture**
* Technology: **microservices**
* GitHub Login: @nishanil
* Microsoft Alias: **nanil**