An example of registering an Authorization middleware in .NET Core

AuthorizationStartup.cs

public class Startup
{
    public IConfiguration Configuration { get; }
    
    public Startup(IConfiguration configuration)
    {
        Configuration = configuration;
    }
    
    public void ConfigureServices(IServiceCollection services)
    {
          // Auth0 configuration
          var domain = auth0Configuration.GetSection("Auth0").GetValue<string>("Domain");

          // Add Authorization service/handler
          services.AddAuthorization(
              options =>
              {
                  options.AddPolicy(
                      "admin",
                      // See https://auth0.com/docs/quickstart/backend/aspnet-core-webapi/01-authorization#validate-scopes for details
                      policy => policy.Requirements.Add(new HasScopeRequirement(domain, "admin"))
                  );
              }
          );
          // See https://auth0.com/docs/quickstart/backend/aspnet-core-webapi/01-authorization#validate-scopes for details
          services.AddSingleton<IAuthorizationHandler, HasScopeHandler>();
          
          // ... other service registration omitted for brevity
    }
    
    public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
    {
        // Add Authorization middleware
        app.UseAuthorization();
        
        // ... other configuration omitted for brevity
    }
}