Modern business applications use complex communication patterns in the backend. Multiple microservices might be involved. Machine-to-machine communication might be implemented using message bus systems. Certain aspects of transaction processing might be handled by event-driven, serverless functions.

Working with a backend like that is a challenge for UI developers, especially in the browser. A Blazor front-end for instance could send a business transaction to a backend-for-frontend (BFF) webserver. Yet, it will not immediately get the result of the transaction. Technically, the BFF server will response to the UI's HTTP request but from a user's perspective, this is not the business transaction's result. It might take a while until the result she is interested in will become available.

This sample demonstrates how UI developers can make use of Azure's serverless capabilities to implement a BFF layer (C#) for a Blazor app. It uses Azure's SignalR service to push messages from the server to the client without having to implement its own Websocket or SignalR service.

I presented this sample at the .NET Meetup Vienna on August 25th 2020. Here you can find the recording (English):

I created a TypeScript/Node.js/Angular version of the sample, too. You can find it on GitHub.