How to design a Repository Pattern with Dependency Injection in ASP.NET Core MVC?

Question

Being fairly new to ASP.NET Core 1.0 MVC, I have decided to use a Repository Pattern for an MVC Core app; I'm using a SQL DB for the Data Layer SampleDbContext, and I want to have a Repository class for some of my business Entities. So far I have done the following in thestartup.cs, CustomerController.cs and CustomerRepository.cs files, where a sample Entity is "Customer".

In the ConfigureServices method of the Startup Class:

public void ConfigureServices(IServiceCollection services) {     services.AddDbContext<SampleDbContext>(options =>        options.UseSqlServer(Configuration.GetConnectionString("SampleDB"))); } 

In a Controller:

public class CustomerController : Controller {      private SampleDBContext _context;     private CustomerRepository = new CustomerRepository (new SampleDBContext());      public CustomerController(SampleDBContext context)     {         _context = context;     } } 

In a Repository:

public class CustomerRepository {     private SampleDBContext _context;      public CustomerRepository(SampleDBContext context)     {         _context = context;     } } 

With this design, I plug in the SampleDbContext as a service in the startup.cs once, and then for each Controller (that receives Dependency Injection) I instantiate a corresponding Repository passing along a new instance of the SampleDbContext. Is this repetitive instantiation of the DB context a good design for a multi-user environment? I suppose I could add each Repository as a service to the startup.cs but that doesn't look nice. Please tell me a good design implementation for my case, or put me in the right track if I'm lost.

Answer 1

You can see simple example how to use repository pattern:

You create repository interface:

using System.Collections.Generic;  namespace TodoApi.Models {     public interface ITodoRepository     {         void Add(TodoItem item);         IEnumerable<TodoItem> GetAll();         TodoItem Find(long key);         void Remove(long key);         void Update(TodoItem item);     } } 

Then implement it:

using System; using System.Collections.Generic; using System.Linq;  namespace TodoApi.Models {     public class TodoRepository : ITodoRepository     {         private readonly TodoContext _context;          public TodoRepository(TodoContext context)         {             _context = context;             Add(new TodoItem { Name = "Item1" });         }          public IEnumerable<TodoItem> GetAll()         {             return _context.TodoItems.ToList();         }          public void Add(TodoItem item)         {             _context.TodoItems.Add(item);             _context.SaveChanges();         }          public TodoItem Find(long key)         {             return _context.TodoItems.FirstOrDefault(t => t.Key == key);         }          public void Remove(long key)         {             var entity = _context.TodoItems.First(t => t.Key == key);             _context.TodoItems.Remove(entity);             _context.SaveChanges();         }          public void Update(TodoItem item)         {             _context.TodoItems.Update(item);             _context.SaveChanges();         }     } } 

Then register in ConfigureServices:

services.AddSingleton<ITodoRepository, TodoRepository>(); 

Then inject it to Controller:

namespace TodoApi.Controllers {     [Route("api/[controller]")]     public class TodoController : Controller     {         public TodoController(ITodoRepository todoItems)         {             TodoItems = todoItems;         }         public ITodoRepository TodoItems { get; set; }     } }