How do we access a non-static variable without the need for instantiation? Entity Framework - ASP. Net Core

Question

In the EFStoreRepository class, I have a variable of StoreDbContext type(context)

StoreDbContext class and Products field inside it are not static. but I can call Products without instantiating the StoreDbContext class like a static field.

How do we access a non-static field without the need for instantiation?

using Microsoft.AspNetCore.Mvc;
using SportsStore.Models;

namespace SportsStore.Controllers
{
     public class HomeController : Controller
     {
          private IStoreRepository repository;
        public HomeController(IStoreRepository repo)
        {
               repository = repo;
        }
        public IActionResult Index()
          {
               return View(repository.Products);
          }
     }
}

using Microsoft.EntityFrameworkCore;

namespace SportsStore.Models
{

     public static class SeedData
     {

          public static void EnsurePopulated(IApplicationBuilder app)
          {
               StoreDbContext context = app.ApplicationServices
                   .CreateScope().ServiceProvider.GetRequiredService<StoreDbContext>();

               if (context.Database.GetPendingMigrations().Any())
               {
                    context.Database.Migrate();
               }

               if (!context.Products.Any())
               {
                    context.Products.AddRange(
                        new Product
                        {
                             Name = "Kayak",
                             Description = "A boat for one person",
                             Category = "Watersports",
                             Price = 275
                        },
                        new Product
                        {
                             Name = "Lifejacket",
                             Description = "Protective and fashionable",
                             Category = "Watersports",
                             Price = 48.95m
                        },
                        new Product
                        {
                             Name = "Soccer Ball",
                             Description = "FIFA-approved size and weight",
                             Category = "Soccer",
                             Price = 19.50m
                        },
                        new Product
                        {
                             Name = "Corner Flags",
                             Description = "Give your playing field a professional touch",
                             Category = "Soccer",
                             Price = 34.95m
                        },
                        new Product
                        {
                             Name = "Stadium",
                             Description = "Flat-packed 35,000-seat stadium",
                             Category = "Soccer",
                             Price = 79500
                        },
                        new Product
                        {
                             Name = "Thinking Cap",
                             Description = "Improve brain efficiency by 75%",
                             Category = "Chess",
                             Price = 16
                        },
                        new Product
                        {
                             Name = "Unsteady Chair",
                             Description = "Secretly give your opponent a disadvantage",
                             Category = "Chess",
                             Price = 29.95m
                        },
                        new Product
                        {
                             Name = "Human Chess Board",
                             Description = "A fun game for the family",
                             Category = "Chess",
                             Price = 75
                        },
                        new Product
                        {
                             Name = "Bling-Bling King",
                             Description = "Gold-plated, diamond-studded King",
                             Category = "Chess",
                             Price = 1200
                        }
                    );
                    context.SaveChanges();
               }
          }
     }
}

using SportsStore.Models;
using Microsoft.EntityFrameworkCore;
internal class Program

{
     private static void Main(string[] args)
     {
          var builder = WebApplication.CreateBuilder(args);
          builder.Services.AddControllersWithViews();
          builder.Services.AddDbContext<StoreDbContext>(opts =>
          {
               opts.UseSqlServer(builder.Configuration["ConnectionStrings:SportsStoreConnection"]);
          });

          builder.Services.AddScoped<IStoreRepository, EFStoreRepository>();

          var app = builder.Build();

          app.UseStaticFiles();
          app.MapDefaultControllerRoute();

          SeedData.EnsurePopulated(app);

          app.Run();
     }
}

using Microsoft.EntityFrameworkCore;

namespace SportsStore.Models
{
     public class StoreDbContext : DbContext
     {
          public StoreDbContext(DbContextOptions<StoreDbContext> options) : base(options) { }
          public DbSet<Product> Products => Set<Product>();
     }
}

using System.ComponentModel.DataAnnotations.Schema;

namespace SportsStore.Models
{
     public class Product
     {
          public long? ProductID { get; set; }
          public string Name { get; set; } = String.Empty;
          public string Description { get; set; } = String.Empty;
          [Column(TypeName = "decimal(8,2)")]
          public decimal Price { get; set; }
          public string Category { get; set; } = String.Empty;
     }
}

namespace SportsStore.Models
{
     public interface IStoreRepository
     {
          IQueryable<Product> Products { get; }
     }
}

namespace SportsStore.Models
{
     public class EFStoreRepository : IStoreRepository
     {
          private StoreDbContext context;
          public EFStoreRepository(StoreDbContext ctx) => context = ctx;
          public IQueryable<Product> Products => context. Products;
     }
}

Answer 1

I edited my question and put all the code in my project. Now could you please tell me who is responsible for providing a StoreDbContext to the constructor in the EFStoreRepository class? I didn't create an instance StoreDbContext.

The simple answer is dependency injection. The code registers the StoreDbContext in the Project.cs file.

builder.Services.AddDbContext<StoreDbContext>(opts =>
{
     opts.UseSqlServer(builder.Configuration["ConnectionStrings:SportsStoreConnection"]);
});

The code also registers the repository service in Project.cs. Order matter here. The StoreDbContext must be registered before the repository.

builder.Services.AddScoped<IStoreRepository, EFStoreRepository>();

Looking at the code above, any constructor that has a IStoreRepository parameter gets a concrete EFStoreRepository type. This is all handled by ASP.NET Core's dependency injection container.

private IStoreRepository repository;
public HomeController(IStoreRepository repo)
{
    repository = repo;
}

Likewise the repository gets a concrete StoreDbContext through constructor injection.

The SeedData class fetches the StoreDbContext directly from the DI contains.

I think you'll be interested in reading the reference documentation

Dependency injection in ASP.NET Core

Answer 2

non-static variables can only be accessed via the instance. static variables are referenced <ClassName>.<VariableName> as they are properties of the class definition.

in your line 7, context is an instance variable, and you are accessing the instance property .Products.