Startup.cs

using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Hosting;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Hosting;
using Microsoft.EntityFrameworkCore;
using Antbear.Models;
using Antbear.Services;

namespace Antbear
{
  public class Startup
  {
    public IConfiguration Configuration { get; }

    public Startup(IConfiguration configuration)
    {
      Configuration = configuration;
    }

    public void ConfigureServices(IServiceCollection services)
    {
      services.AddControllersWithViews();
      services.AddRazorPages();
      services.AddDbContext<AppDbContext>(options =>
        options.UseNpgsql(Configuration.GetConnectionString("Postgres")));
      services.AddScoped<IService<Pet>, PetService>();
    }

    public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
    {
      if (env.IsDevelopment())
      {
        app.UseDeveloperExceptionPage();
      }
      else
      {
        app.UseExceptionHandler("/Error");
        app.UseHsts();
      }
      app.UseStaticFiles();
      app.UseRouting();
      app.UseAuthorization();
      app.UseEndpoints(endpoints =>
      {
        endpoints.MapControllerRoute(
          name: "default",
          pattern: "{controller=Home}/{action=Index}/{id?}"
        );
        endpoints.MapRazorPages();
      });
    }
  }
}