It works: client service + server service + utility service to know server uri when app is running

Program.cs

@@ -1,6 +1,9 @@
+using Sandbox;
 using Sandbox.Components;
 using Sandbox.Models.ViewModels;
 using Sandbox.Services.AuthService;
+using ClientServices = Sandbox.App.Services;
+using ServerServices = Sandbox.Services;
 
 var builder = WebApplication.CreateBuilder(args);
 
@@ -8,8 +11,16 @@ var builder = WebApplication.CreateBuilder(args);
 builder.Services.AddRazorComponents()
     .AddInteractiveServerComponents();
 
+// Blazor client services
+builder.Services.AddScoped<ClientServices.AuthService.IAuthService, ClientServices.AuthService.AuthService>();
+
+// Blazor server services
 builder.Services.AddScoped<IAuthService, AuthService>();
 
+// Get server base address when application starts to properly configure HttpClient for client service to call server service
+builder.Services.AddSingleton<HttpClient>();
+builder.Services.AddSingleton<IHostedService, HttpClientSetupService>();
+
 var app = builder.Build();
 
 // Configure the HTTP request pipeline.
@@ -19,16 +30,18 @@ if (!app.Environment.IsDevelopment())
     // The default HSTS value is 30 days. You may want to change this for production scenarios, see https://aka.ms/aspnetcore-hsts.
     app.UseHsts();
 }
+
 app.UseStatusCodePagesWithReExecute("/not-found", createScopeForStatusCodePages: true);
 app.UseHttpsRedirection();
 
 app.UseAntiforgery();
 
-app.MapPost("/api/register", async (UserRegister request, IAuthService authService) =>
-    await authService.Register(request.Email, request.Password));
+// Blazor server routing
+app.MapPost("/api/auth/register", async (UserRegister request, IAuthService authService) =>
+    await authService.Register(request));
 
 app.MapStaticAssets();
 app.MapRazorComponents<App>()
     .AddInteractiveServerRenderMode();
 
-app.Run();
+app.Run();