(B) Link repos to program.cs

Clinics.Backend/API/Program.cs

 using API.Options.Database;
+using Domain.Repositories.Base;
 using Microsoft.EntityFrameworkCore;
 using Microsoft.Extensions.Options;
 using Persistence.Context;
+using Persistence.Repositories.Base;
 
 var builder = WebApplication.CreateBuilder(args);
 
@@ -30,6 +32,11 @@ builder.Services.AddDbContext<ClinicsDbContext>(
 
 // Add services to the container.
 
+#region Link repositories
+// AddTransient: Created on demand, every time they are requested, not shared across requests or components.
+builder.Services.AddTransient(typeof(IRepository<>), typeof(Repositroy<>));
+#endregion
+
 #region Link controllers with presentation layer
 var presentationAssembly = typeof(Presentation.AssemblyReference).Assembly;
 builder.Services.AddControllers()