Category Archives: Blazor

Adding Logging to Client Side Blazor

Whilst there are some pre-built libraries for this, I seemed to be getting Mono linking errors. What finally worked for me was to install the pre-release versions of:

Install-Package Microsoft.Extensions.Logging -Version 3.0.0-preview6.19304.6
Install-Package Microsoft.Extensions.Logging.Console -Version 3.0.0-preview6.19304.6

Now, in your View Model, accept the Logger:

public MyViewModel(ILogger<MyViewModel> logger)

Then you can log as normal:

_logger.LogInformation("Hello, here's a log message");

You should now see the debug message in the F12 console.

You might be wondering why you don’t need to explicitly inject the logging capability; the reason is that:

BlazorWebAssemblyHost.CreateDefaultBuilder()            

Does that for you.

Using View Models in Blazor

Being new to Blazor (and Razor), the first thing that tripped me up was that the view seemed divorced from the rest of the application. In fact, this is actually quite a nice design, as it forces the use of DI.

For example, say you wanted to create a View Model for your view, you could register that ViewModel in the Startup:

        public void ConfigureServices(IServiceCollection services)
        {
            services.AddTransient<MyViewModel, MyViewModel>();
        }

Note here that you don’t need an interface. If you’re only creating an interface for the purpose of this then that abstraction provides no benefit. That isn’t to say there may not be a reason for having an interface, but if you have one and this is the only place it’s used, you probably should reconsider.

The views in Razor / Blazor (at the time of writing) are *.razor files. In order to resolve the dependency inside the view, you would use the following syntax:

@page "/"
@inject ViewModels.MyViewModel MyViewModel

(Note that @page “/” is only in this snippet to orientate the code.)

You can call initialisation in the view model using something like:

@code {

    protected override async Task OnInitAsync()
    {
        await MyViewModel.Init();
    }    
}

And, within your HTML, you can reference the view model like this:

<div>@MyViewModel.MyData</div>

Magic. Hopefully more to come on Blazor soon.