ClientEvents with strongly typed EventArgs<T> for clients events.

[markdav-is]

We've been using SiteState.Properties.PropertyChanged for intra-module communication with success. As we lean more into messaging between modules the boilerplate and dynamic (loosely typed) objects started to feel fragile. Because we have multiple modules in the same repo, we could share code and created a ClientEvent class (attached). that allows for strongly typed experience.

Let's look at an example:

Publisher Example

[Inject] public ClientEvents ClientEvents { get; set; }
...
    private async Task Launch(MouseEventArgs e)
    {
        XApiMessage xApiMessage = new XApiMessage
        {
            Verb = verb,
            ActivityName = _name,
            ActivityId = _source,
            ModuleId = ModuleState.ModuleId
        };

        // regular way
        SiteState.Properties.XapiMessage = xApiMessage;

        // using ClientEvents 
        await ClientEvents.PublishAsync("XApiMessage", xApiMessage);

    }

Subscriber Example

[Inject] public ClientEvents ClientEvents { get; set; }
...

  protected override void OnInitialized()
  {
      // subscribe to the site state change event
      ((INotifyPropertyChanged)SiteState.Properties).PropertyChanged += PropertyChanged;

      // subscribe to the client event
      ClientEvents.Subscribe<XApiMessage>("XApiMessage", HandleEventAsync);

  }
    // regular way
    async void PropertyChanged(object sender, PropertyChangedEventArgs e)
    {
        // we are looking for changes to the XapiMessage property
        if (e.PropertyName == NotifyPropertyName.XapiMessage)
       {
         // get the new progress
         var xApiMessage = (XApiMessage) SiteState.Properties[NotifyPropertyName.XapiMessage];

         xApiMessage.UserId = PageState.User.UserId;
         xApiMessage.Actor = PageState.User.Email;

         await XApiService.AddMessageAsync(xApiMessage);
       }
    }

     // using ClientEvents 
     private async Task HandleEventAsync(EventArgs<XApiMessage> args)
    {
        var xApiMessage = args.Data;
        xApiMessage.UserId = PageState.User.UserId;
        xApiMessage.Actor = PageState.User.Email;
        await XApiService.AddMessageAsync(xApiMessage);
    }

I know it's not much different, but it does avoid the casting from Dynamic, so it's type-safe.

ClientEvents.cs.txt

[sbwalker]

@markdav-is the current dynamic Properties approach was modeled after a similar approach which exists in other Microsoft UI frameworks (ie. WPF, Silverlight, etc...) which is a well-known developer pattern (sometimes referred to as a PropertyBag).

[markdav-is]

Thanks for the response. We'll keep using it, but I see your point. Maybe I'm being too OOPy, but I like my types!