Updated Blazor WebAssembly app initialization

05 Feb 2020

In the latest preview of client-side Blazor (3.2.0-preview1.20073.1) the project template has been changed to no longer use a Startup.cs approach, but rather to put all initialization in the Main method of Program.cs.

Also, the app builder type has been changed to WebAssemblyHostBuilder.

  public class Program
  {
    public static async Task Main(string[] args)
    {
      var builder = WebAssemblyHostBuilder.CreateDefault(args);
      builder.RootComponents.Add<App>("app");

      await builder.Build().RunAsync();
    }
  }

This affects CSLA .NET, because the previous app initialization support was based around the Startup.cs model, similar to ASP.NET Core server apps.

The updated approach is actually quite nice, in that all CSLA configuration is handled by a single call to UseCsla:

  public class Program
  {
    public static async Task Main(string[] args)
    {
      var builder = WebAssemblyHostBuilder.CreateDefault(args);
      builder.RootComponents.Add<App>("app");

      builder.UseCsla();

      await builder.Build().RunAsync();
    }
  }

This new UseCsla method adds all necessary services to the IoC container, and does all required client-side configuration of CSLA to work within Blazor WebAssembly.

An overload supports additional configuration. For example:

  builder.UseCsla(
    (config) => config
      .DataPortal()
        .DefaultProxy(typeof(Csla.DataPortalClient.HttpProxy), "https://myserver/api/dataportal"));

I rather like the fact that Microsoft has changed the template so it doesn’t seem so “server-like”, given that Blazor WebAssembly is a smart client app, not a server app. This app initialization scheme is more similar to what you’d see in WPF or UWP, and that’s fine with me.