Open the Startup.cs file.

Note the ConfigureServices method that adds support for MVC along with other framework and application services such as ASP.NET Identity, as shown in the following code:

    public void ConfigureServices(IServiceCollection services) 
    { 
      // Add framework services. 
      services.AddDbContext<ApplicationDbContext>(options => 
        options.UseSqlServer(Configuration 
        .GetConnectionString("DefaultConnection"))); 
   
      services.AddIdentity<ApplicationUser, IdentityRole>() 
        .AddEntityFrameworkStores<ApplicationDbContext>() 
        .AddDefaultTokenProviders(); 
 
      services.AddMvc(); 
 
      // Add application services. 
      services.AddTransient<IEmailSender, AuthMessageSender>(); 
      services.AddTransient<ISmsSender, AuthMessageSender>(); 
    } 

Next, we have the Configure method. Note the following:

    public void Configure(IApplicationBuilder app,  
      IHostingEnvironment env, ILoggerFactory loggerFactory) 
    { 
      loggerFactory.AddConsole(Configuration.GetSection("Logging")); 
      loggerFactory.AddDebug(); 
 
      if (env.IsDevelopment()) 
      { 
        app.UseDeveloperExceptionPage(); 
        app.UseDatabaseErrorPage(); 
        app.UseBrowserLink(); 
      } 
      else 
      { 
        app.UseExceptionHandler("/Home/Error"); 
      } 
 
      app.UseStaticFiles(); 
 
      app.UseIdentity(); 
 
      app.UseMvc(routes => 
      { 
        routes.MapRoute( 
          name: "default", 
          template: "{controller=Home}/{action=Index}/{id?}"); 
      }); 
    } 

The default route looks at any URL entered by the user in the address bar and matches it to extract the name of a controller, the name of an action, and an optional id value (the ? symbol makes it optional). If the user hasn't entered these names, it uses defaults of Home for the controller and Index for the action (the = assignment sets a default for a named segment).

Contents in curly-brackets {} are called segments, and they are like a named parameter of a method. The value of these segments can be any string.

The responsibility of a route is to discover the name of a controller and an action.

The following table contains example URLs and how MVC would work out the names:

Note that if the user does not supply a name, then the defaults, Home and Index, are used as specified when the route was registered. You could change these defaults if you wanted.