Derivative Webhook with SignalR (.NET)

December 13, 2018

Derivative webhook was introduced early this year, and it was later included on the .NET SDK, see basic code snippet here. But what about a more complete sample?

Before we dive into a sample, we need a way to push updates to the browser client, and that's where we can use SignalR. There a few resources out there, but I liked this video.

SignalR requires:

1. Client JavaScript to connect and handle messages from the server. The video uses a package from NPM, which is an option, but for simplicity, I like to use CDNs, like:

<script src="//unpkg.com/@aspnet/signalr@1.1.0/dist/browser/signalr.min.js"></script>

2. Server hub to manage the connection, where we can implement methods to receive messages from the client (which we're not using here). For this case, we need a way to identify the client connection id and, to keep it organized, a static function to encapsulate the feature.

public class ModelDerivativeHub : Microsoft.AspNetCore.SignalR.Hub
{
    public string GetConnectionId() { return Context.ConnectionId; }

    public async static Task ExtractionFinished(IHubContext<ModelDerivativeHub> context, JObject body)
    {
        string connectionId = body["hook"]["scope"]["workflow"].Value<String>();
        await context.Clients.Client(connectionId).SendAsync("extractionFinished", body);
    }
}

And here you see the trick: I'm using the connectionId (which uniquely identifies a client) as my workflow id, so when a translation is done I know which client browser to notify.

That's it, basically. 

You can see it running at modelderivative.herokuapp.com or see this specific commit (with all changes) here.

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Augusto Goncalves
Developer Advocate, Autodesk

Developer Advocate at Autodesk since 2008, working with both desktop and web/cloud apps using top technologies, like C#, JavaScript, NodeJS and any other that can solve problems and improve workflo