title: IComponentsApplicationBuilder type cannot be found in the Startup class of Blazor
body: <p>I am trying to learn Blazor by following a tutorial. The tutorial created a singleton service in the "Client" that needs to be declared in the Startup class. The problem is in my end, I get an error in the part of <code>IComponentsApplicationBuilder</code>. This is the whole code of the Startup.</p>
  
  <pre><code>using Microsoft.Extensions.DependencyInjection;
  
  namespace BlazorMovies.Client
  {
      public class Startup
      {
          public void ConfigureServices(IServiceCollection services)
          {
              services.AddSingleton&lt;SingletonService&gt;();
              services.AddTransient&lt;TransientService&gt;();
          }
  
          public void Configure(IComponentsApplicationBuilder app)
          {
              app.AddComponent&lt;App&gt;("app");
          }
      }
  }
  </code></pre>
  
  <p><a href="https://i.stack.imgur.com/FWGcK.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/FWGcK.png" alt="enter image description here"></a></p>
  
  <p>Could you please show me how to correct this? Thank you.</p>