Rx.NET VS MockQueryable

One of the greatest things i discovered recently, is Reactive programming / Reactive Extensions ( https://github.com/dotnet/reactive ).

https://github.com/dotnet/reactive has a lot of different time related extensions for "events". Maybe you'll find something for yourself, if you google for rate limiting with reactive.

Install Reactive Extensions: https://github.com/dotnet/reactive

Another option is to use the RxJava library in Java. This library uses reactive programming principles to make it easy to write asynchronous and event-driven code. It's particularly well-suited for handling streams of data and allows you to write code that is both efficient and easy to read.

I'd use a dedicated event bus based on Reactive Extensions or MediatR to publish domain events from your domain services. This probably doesn't solve all your ViewModel update problems as is, maybe you need to revise the granularity (maybe you can have smaller ViewModels that refresh single property that exposes the Model) and lifespan (sometimes you can create a ViewModel, make it perform it's task and then discard it completely) of your ViewModels.

If you're finding yourself in a situation where you need to turn this behavior into a pattern because there are a lot of View Models that need to execute async business logic in response to some changes, I'd go with something like MediatR or Reactive Extensions. The idea is, again, that some other, probably business-level, component listens to changes in a decoupled way (that means it doesn't subscribe directly to your View Model, but to an event bus instead). View Model publishes change events to the event bus, and business-component reacts to these events by executing the business logic.

We'd really appreciate if it consumers of the library could update and provide any issues / bugs via the GitHub repo: https://github.com/dotnet/reactive/issues

The repository proponents are mostly trying to reduce the interface you need to mock in order to test your business logic, especially with unit testing, not integration testing. If you're just depending on the db context, (and you're mocking with the really awesome MockQueryable library) the tester needs to know exactly which parts of the db context are being used. This is not how unit testing should work. When writing unit tests, you shouldn't have to know that much about the internal behaviour of the thing you are trying to mock.