Blazor/Razor Class Library. Dependency Injection

Question

I am confused on how to use a Razor Class Library that requires injected objects. I created a new razor class library project. There is no program.cs file and hence no WebAssemblyHostBuilder to add services to? How do I inject dependencies into the components?

Answer 1

A library is simply that. It's not an application. You load the DI objects in the application project. You can write extension classes in your library as a wrapper to load all the necessary objects. builder.Services.AddServerSideBlazor() is just such an extension.

Here's an example extension method for the Weather Forecast.

    public static class ServiceCollectionExtensions
    {
        public static void AddWeatherServices(this IServiceCollection services)
        {
            services.AddSingleton<WeatherForecastService>();
        }
    }

And use it in the application startup:

// Add services to the container.
builder.Services.AddRazorPages();
builder.Services.AddServerSideBlazor();
builder.Services.AddWeatherServices();

You inject the services into your components as normal. If you use a component in an application and the necessary services aren't loaded the page on which the component is being used will throw an error.