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Share my dbContext with all my repository/service class?

I'm working on a classic .Net Framework Web API solution.
I have 3 layers. Let's call them
MVC - with POST, GET, UPDATE, DELETE controllers.
BIZZ - for business with my service class. My service class are king of repositories with CREATE, READ, UPDATE, DELETE and specific methods.
DATA - with POCO and definition of DB context.
I will not develop the EF layer. It is a classic Entity Framework project with POCO.Here is a sample of a Service and with BaseService class
public abstract class Service : IDisposable
{
protected DbContext dbContext = new DbContext();
public void Dispose()
{
dbContext.Dispose();
}
}
Then I have a cart service and a order service. They are similar in their structure so I will only write the code useful for this example.
public class CartService : Service
{
public Cart Create(Cart cart)
{
// Create the cart
}
public Cart Read(Guid id)
{
// Read
}
public Cart Update(Cart cart)
{
// I do some check first then
}
public void Delete(Cart cart)
{
// Delete
}
public void Checkout(Cart cart)
{
// Validation of cart removed in this example
dbContext.Cart.Attach(cart);
cart.DateCheckout = DateTime.UtcNow;
dbContext.Entry(cart).State = EntityState.Modified; // I think this line can be removed
dbContext.SaveChanges();
using (var orderService = new OrderService())
{
foreach (var order in cart.Orders)
{
order.DateCheckout = cart.DateCheckout;
order.Status = OrderStatus.PD; // pending
orderService.Update(order);
}
}
}
}
public class OrderService : Service
{
public Cart Create(Cart cart)
{
// Create the cart
}
public Cart Read(Guid id)
{
// Read
}
public Cart Update(Cart cart)
{
dbContext.Entry(order).State = EntityState.Modified;
dbContext.SaveChanges();
// More process here...
return order;
}
public void Delete(Cart cart)
{
// Delete
}
}
So, I have a service, cart service, that call another service, order service. I must work like this because I cannot simply accept the cart and all orders in it as it is. When I save a new order or update an existing order I must create a record in some other tables in other databases. The code is not in my example. So, I repeat I have a service that call another service and then I have 2 dbContext. At best this just create 2 context in memory, at worst this create exception. Exception like you cannot attach an entity to 2 contexts or this entity is not in context.
Well, I would like all my service use the same context. I suppose you will al tell me to use Dependency Injection. Yes, well ok but I don't want, each time I create a new service have to pass the context. I don't want to have to do that:
public void Checkout(Cart cart)
{
// ...
using (var orderService = new OrderService(dbContext))
{
// ...
}
}
I would like to do something that impact my base service only if possible. A singleton maybe... At this point I can see your face. Yes I know Singleton are soo bad. Yes but i'm doing a IIS Web API. Each request is a new instance. I don't care about the impact of the singleton. And I can load my database by changing the connection string in config file so the benefit of DI is there already. Well, I also know it is possible to have singleton with DI. I just don't know how.
So, what can I do to be sure I share my dbContext with all my services?

Disclaimer: This example is not intended to be a "good" one and certainly does not follow best practices, but faced with an existing legacy code base which from your example already suffers from a number of questionable practices, this should get you past the multiple context issues.
Essentially if you're not already using a IoC Container to perform dependency injection then what you need is to introduce a unit of work to manage the scope of a DbContext where your base Service class provides a DbContext provided by the unit of work. (Essentially a DbContext Registry)
For the unit of work and assuming EF6 I would recommend Mehdime's DbContextScope which is available as a NuGet package. Alternatively you can find the source code on Github and implement something similar without too much trouble. I like this pattern because it leverages the CallContext to serve as the communication layer between the ContextScope (Unit of Work) created by the DbContextScopeFactory and the AmbientDbContextScope. This will probably take a little time to get your head around but it injects very nicely into legacy applications where you want to leverage the Unit of Work and don't have dependency injection.
What it would look like:
In your Service class you would introduce the AmbientDbContextLocator to resolve your DbContext:
private readonly IAmbientDbContextLocator _contextLocator = new AmbientDbContextLocator();
protected DbContext DbContext
{
get { return _contextLocator.Get<DbContext>(); }
}
And that's it. Later as you refactor to accommodate Dependency injection, just inject the AmbientDbContextLocator instead of 'new'ing it up.
Then, in your web API controllers where you are using your services, (not the services themselves) you need to add the DbContextScopeFactory instance..
private readonly IDbContextScopeFactory _contextScopeFactory = new DbContextScopeFactory();
Lastly, in your API methods, when you want to call your services, you need to simply use the ContextScopeFactory to create a context scope. The AmbientDbContextLocators will retrieve the DbContext from this context scope. The context scope you create with the factory will be done in a using block to ensure your contexts are disposed. So, using your Checkout method as an example, it would look like:
In your Web API [HttpPost] Checkout() method:
using (var contextScope = _contextScopeFactory.Create())
{
using(var service = new CartService())
{
service.Checkout();
}
contextScope.SaveChanges();
}
Your cart service Checkout method would remain relatively unchanged, only instead of accessing dbContext as a variable (new DbContext()) it will access the DbContext property which gets the context through the context locator.
The Services can continue to call DbContext.SaveChanges(), but this isn't necessary and the changes will not be committed to the DB until the contextScope.SaveChanges() is called. Each service will have its own instance of the Context Locator rather than the DbContext and these will be dependent on you defining a ContextScope to function. If you call a Service method that tries to access the DbContext without being within a using (var contextScope = _contextScopeFactory.Create()) block you will receive an error. This way all of your service calls, even nested service calls (CartService calls OrderService) will be interacting with the same DbContext instance.
Even if you just want to read data, you can leverage a slightly faster DbContext using _contextScopeFactory.CreateReadOnly() which will help guard against unexpected/disallowed calls to SaveChanges().

When using the ASP.NET Core stack, the tutorial for using EF with it defaults to using DI to provide your DB context, just not with a service layer. That said, it actually does the right thing for this out of the box. I'll give a brief rundown of the bare minimum necessary for this to work, using whatever the latest versions of ASP.NET Core Web API and EF Core were on NuGet at the time of writing.
First, let's get the boilerplate out of the way, starting with the model:
Models.cs
public class ShopContext : DbContext
{
public ShopContext(DbContextOptions options) : base(options) {}
// We add a GUID here so we're able to tell it's the same object later.
public string Id { get; } = Guid.NewGuid().ToString();
public DbSet<Cart> Carts { get; set; }
public DbSet<Order> Orders { get; set; }
}
public class Cart
{
public string Id { get; set; }
public string Name { get; set; }
}
public class Order
{
public string Id { get; set; }
public string Name { get; set; }
}
Then some bare-bones services:
Services.cs
public class CartService
{
ShopContext _ctx;
public CartService(ShopContext ctx)
{
_ctx = ctx;
Console.WriteLine($"Context in CartService: {ctx.Id}");
}
public async Task<List<Cart>> List() => await _ctx.Carts.ToListAsync();
public async Task<Cart> Create(string name)
{
return (await _ctx.Carts.AddAsync(new Cart {Name = name})).Entity;
}
}
public class OrderService
{
ShopContext _ctx;
public OrderService(ShopContext ctx)
{
_ctx = ctx;
Console.WriteLine($"Context in OrderService: {ctx.Id}");
}
public async Task<List<Order>> List() => await _ctx.Orders.ToListAsync();
public async Task<Order> Create(string name)
{
return (await _ctx.Orders.AddAsync(new Order {Name = name})).Entity;
}
}
The only notable things here are: the context comes in as a constructor parameter as God intended, and we log the ID of the context to verify when it gets created with what.
Then our controller:
ShopController.cs
[ApiController]
[Route("[controller]")]
public class ShopController : ControllerBase
{
ShopContext _ctx;
CartService _cart;
OrderService _order;
public ShopController(ShopContext ctx, CartService cart, OrderService order)
{
Console.WriteLine($"Context in ShopController: {ctx.Id}");
_ctx = ctx;
_cart = cart;
_order = order;
}
[HttpGet]
public async Task<IEnumerable<string>> Get()
{
var carts = await _cart.List();
var orders = await _order.List();
return (from c in carts select c.Name).Concat(from o in orders select o.Name);
}
[HttpPost]
public async Task Post(string name)
{
await _cart.Create(name);
await _order.Create(name);
await _ctx.SaveChangesAsync();
}
}
As above, we take the context as a constructor parameter to triple-check it's what it should be; we also need it to call SaveChanges at the end of an operation. (You can refactor this out of controllers if you want to, but they'll work just fine as units of work for now.)
The part that ties this together is the DI configuration:
Startup.cs
public void ConfigureServices(IServiceCollection services)
{
services.AddControllers();
// Use whichever provider you have here, this is where you grab a connection string from the app configuration.
services.AddDbContext<ShopContext>(options =>
options.UseInMemoryDatabase("Initrode"));
services.AddScoped<CartService>();
services.AddScoped<OrderService>();
}
AddDbContext() defaults to registering a DbContext to be created per-request by the container. Web API provides the AddControllers method that puts those into the DI container, and we also register our services manually.
The rest of Startup.cs I've left as-is.
Starting this up and opening https://localhost:5001/shop should log something like:
Context in CartService: b213966e-35f2-4cc9-83d1-98a5614742a3
Context in OrderService: b213966e-35f2-4cc9-83d1-98a5614742a3
Context in ShopController: b213966e-35f2-4cc9-83d1-98a5614742a3
with the same GUID for all three lines in a request, but a different GUID between requests.
A little additional explanation of what goes on above:
Registering a component in a container (using Add() and such above) means telling the container those components exist and that it should create them for you when asked, as well as what identifiers they're available under and how to create them. The defaults for this are more or less "make the component available as its class, and create it by calling its one public constructor, passing other registered components into it" - the container looks at the constructor signature to figure this out.
"Scoped" in an ASP.NET Core app means "per-request." I think in this case one could also use services with a transient lifetime - a new one created every time it's needed, but they'll still get the same DbContext as long as they're created while handling the same request. Which one to do is a design consideration; the main constraint is that you can't inject shorter-lived components into longer-lived components without having to use more complex techniques, which is why I favour having all components as short-lived as possible. In other words, I only make things longer-lived when they actually hold some state that needs to live for that time, while also doing that as sparingly as possible because state bad. (Just recently I had to refactor an unfortunate design where my services were singletons, but I wanted my repositories to be per-request so as to be able to inject the currently logged in user's information into the repository to be able to automatically add the "created by" and "updated by" fields.)
You'll note that with support for doing things this way being built-in to both ASP.NET Core and EF Core, there's actually very little extra code involved. Also, the only thing needed to go from "injecting a context into your controllers" (as the tutorial does) to "injecting a context into services that you use from your controllers" is adding the services into DI - since the controller and context are already under DI, anything new you add can be injected into them and vice versa.
This should give you a quick introduction into how to make things "just work" and shows you the basic use case of a DI container: you declaratively tell it or it infers "this is an X", "this is an Y", "this is a Z and it needs to be created using an X and a Y"; then when you ask the container to give you a Z, it will automagically first create an X and Y, then create Z with them. They also manage the scope and lifetime of these objects, i.e. only create one of a type for an API request. Beyond that it's a question of experience with them and familiarity with a given container - say Ninject and Autofac are much more powerful than the built-in one - but it's variations on the same idea of declaratively describing how to create an object possibly using other objects (its dependencies) and having the container "figure out" how to wire things together.

Transaction Scope for different repository classes

I'm trying to wrap a transaction around 2 or more database operations which occur in different repository classes. Each repository class uses a DbContext instance, using Dependency Injection. I'm using Entity Framework Core 2.1.
public PizzaService(IPizzaRepo pizzaRepo, IPizzaIngredientsRepo ingredientRepo)
{
_pizzaRepo = pizzaRepo;
_ingredientRepo = ingredientRepo;
}
public async Task SavePizza(PizzaViewModel pizza)
{
using (var scope = new TransactionScope(TransactionScopeOption.Required, new TransactionOptions { IsolationLevel = IsolationLevel.ReadCommitted }))
{
int pizzaRows = await _pizzaRepo.AddEntityAsync(pizza.Pizza);
int ingredientRows = await _ingredientRepo.PutIngredientsOnPizza(
pizza.Pizza.PizzaId,
pizza.Ingredients.Select(x => x.IngredientId).ToArray());
scope.Complete();
}
}
}
Obviously, if one of the operations fails, I want to rollback the entire thing.
Will this transaction scope be enough to rollback or should the repository classes have transactions on their own?
Even if above methods works, are there better ways to implement transactions?

Repository patterns are great for enabling testing, but do not have a repository new up a DbContext, share the context across repositories.
As a bare-bones example (assuming you are using DI/IoC)
The DbContext is registered with your IoC container with a lifetime scope of Per Request. So at the onset of the service call:
public PizzaService(PizzaDbContext context, IPizzaRepo pizzaRepo, IPizzaIngredientsRepo ingredientRepo)
{
_context = pizzaContext;
_pizzaRepo = pizzaRepo;
_ingredientRepo = ingredientRepo;
}
public async Task SavePizza(PizzaViewModel pizza)
{
int pizzaRows = await _pizzaRepo.AddEntityAsync(pizza.Pizza);
int ingredientRows = await _ingredientRepo.PutIngredientsOnPizza(
pizza.Pizza.PizzaId,
pizza.Ingredients.Select(x => x.IngredientId).ToArray());
_context.SaveChanges();
}
Then in the repositories:
public class PizzaRepository : IPizzaRepository
{
private readonly PizzaDbContext _pizzaDbContext = null;
public PizzaRepository(PizzaDbContext pizzaDbContext)
{
_pizzaDbContext = pizzaDbContext;
}
public async Task<int> AddEntityAsync( /* params */ )
{
PizzaContext.Pizzas.Add( /* pizza */)
// ...
}
}
The trouble I have with this pattern is that it restricts the unit of work to the request, and only the request. You have to be aware of when and where the context save changes occurs. You don't want repositories for example to call SaveChanges as that could have side effects depending on what was changed as far as the context goes prior to that being called.
As a result I use a Unit of Work pattern to manage the lifetime scope of the DbContext(s) where repositories no longer get injected with a DbContext, they instead get a locator, and the services get a context scope factory. (Unit of work) The implementation I use for EF(6) is Mehdime's DbContextScope. (https://github.com/mehdime/DbContextScope) There are forks available for EFCore. (https://www.nuget.org/packages/DbContextScope.EfCore/) With the DBContextScope the service call looks more like:
public PizzaService(IDbContextScopeFactory contextScopeFactory, IPizzaRepo pizzaRepo, IPizzaIngredientsRepo ingredientRepo)
{
_contextScopeFactory = contextScopeFactory;
_pizzaRepo = pizzaRepo;
_ingredientRepo = ingredientRepo;
}
public async Task SavePizza(PizzaViewModel pizza)
{
using (var contextScope = _contextScopeFactory.Create())
{
int pizzaRows = await _pizzaRepo.AddEntityAsync(pizza.Pizza);
int ingredientRows = await _ingredientRepo.PutIngredientsOnPizza(
pizza.Pizza.PizzaId,
pizza.Ingredients.Select(x => x.IngredientId).ToArray());
contextScope.SaveChanges();
}
}
Then in the repositories:
public class PizzaRepository : IPizzaRepository
{
private readonly IAmbientDbContextLocator _contextLocator = null;
private PizzaContext PizzaContext
{
get { return _contextLocator.Get<PizzaContext>(); }
}
public PizzaRepository(IDbContextScopeLocator contextLocator)
{
_contextLocator = contextLocator;
}
public async Task<int> AddEntityAsync( /* params */ )
{
PizzaContext.Pizzas.Add( /* pizza */)
// ...
}
}
This gives you a couple benefits:
The control of the unit of work scope remains clearly in the service. You can call any number of repositories and the changes will be committed, or rolled back based on the determination of the service. (inspecting results, catching exceptions, etc.)
This model works extremely well with bounded contexts. In larger systems you may split different concerns across multiple DbContexts. The context locator serves as one dependency for a repository and can access any/all DbContexts. (Think logging, auditing, etc.)
There is also a slight performance/safety option for Read-based operations using the CreateReadOnly() scope creation in the factory. This creates a context scope that cannot be saved so it guarantees no write operations get committed to the database.
The IDbContextScopeFactory and IDbContextScope are easily mock-able so that your service unit tests can validate if a transaction is committed or not. (Mock an IDbContextScope to assert SaveChanges, and mock an IDbContextScopeFactory to expect a Create and return the DbContextScope mock.) Between that and the Repository pattern, No messy mocking DbContexts.
One caution that I see in your example is that it appears that your View Model is serving as a wrapper for your entity. (PizzaViewModel.Pizza) I'd advise against ever passing an entity to the client, rather let the view model represent just the data that is needed for the view. I outline the reasons for this here.

What can i test on these types of methods?

Sorry for this orrible title, i did my best.
Maybe someone with more imagination can help me and this title.
I am a newbie in Unit Testing and I am a bit lost. I am reading "The Art of Unit Tesing" anyway.
I am using Entity Framework 6 for a WebApi application.
In this applicantion i use this pattern:
Api calls Service that calls Repository that return data to service that return data to API.
So, I have a tons of this methods:
API:
public async Task<IHttpActionResult> GetUserById(Guid id)
{
try
{
UserService userService = new UserService();
return Ok(await userService.GetById(id));
}
catch(Exception ex)
{
return InternalServerError(ex);
}
}
Service:
public class UserService
{
private IUserRepository userRepo;
public IUserRepository userRepo { get => userRepo; set => userRepo = value }
public async Task<AspNetUser> GetById(Guid id)
{
if(id == Guid.Empty() || id == null)
return null;
return await Task.Run(() => userRepo.GetById(id));
}
}
Repo:
public interface IUserRepository
{
Task<AspNetUser> GetById(Guid id);
}
public class UserRepository: IUserRepository
{
public async Task<AspNetUser> GetById(Guid id)
{
return DbSet.Where(i => i.Id == id).FirstOrDefault();
}
}
What can be faulty here? what can go wrong? What i should test?

The goal of unit testing is to test each module (usually equates to a method) of code in isolation. This is only possible with loose coupling. In your existing code you do not use DI (dependency injection) and you instantiate service / repository classes in your methods. This makes testing this code in isolation difficult if not almost impossible. Writing unit tests often reveals design/code flaws like these. Refactor your code as follows:
Use interfaces, you did it on your repository but not on your service but that is actually the best place to use an interface.
Use dependency injection. This will make testing much easier.
Why are you using a repository pattern around EF? EF's DbSet is a generic implementation of a repository pattern and DbContext is an implementation of Unit of Work. I strongly recommend not trying to re-encapsolate these in your own half baked abstractions, you are only going to end up making it more difficult for your self to use your own constructs.
That is not the correct way to use async/await. Call through to an async method and if non exists then do not create an async method to begin with (this does not apply to cases where you want to use TPL). In your case you should call through to FirstOrDefaultAsync (or possible SingleOrDefaultAsync);
Name your async methods with the suffix Async, this is considered proper convention.
UserController.cs
private readonly IUserService userService;
public UserController(IUserService userService){
this.userService = userService;
}
public async Task<IHttpActionResult> GetUserById(Guid id)
{
try
{
return Ok(await userService.GetByIdAsync(id));
}
catch(Exception ex)
{
return InternalServerError(ex);
}
}
UserService.cs
public interface IUserService{
Task<AspNetUser> GetByIdAsync(Guid id);
}
public class UserService : IUserService
{
// you can leave MyDbContext unsealed or you can use an interface on this as well depending on your needs
private readonly MyDbContext dbContext;
public UserService(MyDbContext dbContext) {
this.dbContext = dbContext;
}
public Task<AspNetUser> GetByIdAsync(Guid id)
{
if(id == Guid.Empty())
return Task.FromResult(null as AspNetUser);
return dbContext.AspNetUsers.SingleOrDefaultAsync(user => user.Id == id);
}
}
Having done this now you can unit test your code. You can use a popular fake/mock/substitute framework and do the following:
Create a test for your api's GetUserById by creating a mock IUserService instance with custom behavior on GetByIdAsync
Create a test for the UserService::GetByIdAsync method by creating a mock of MyDbContext, you can supply a collection of AspNetUser instances and test which one is returned when calling the method or even test the expression that the DbSet is called with.
As far as what you should test depends on possible inputs and the corresponding expected results. For example : What happens when you pass in an empty GUID into GetByIdAsync? What does the API do when a null result is returned in the Task? etc.

Frankly, this is likely NOT the "best" answer here and I am up voting others.
As this is getting a bit "long" for comments so I am posting as an answer with the "what" more so than the "how" here as Igor has done - good stuff there!
This will be somewhat generic in that regard.
Test what I call the "happy path" i.e. a valid GUID (in your instance) gets something valid.
Perhaps something valid from a string:
Guid g = new Guid("11223344-5566-7788-99AA-BBCCDDEEFF00");
Test something invalid (not present for example)
Guid g = new Guid(someinvalidthingthatparses);
New:
Guid g = Guid.NewGuid();
all 0's i.e. Guid.Empty
Test uninitiated values
In a perfect world, some of these should not get to the method being tested but what if they do? How does it react?
To extrapolate further, I digress but if you are testing something for example that passes an integer as Int32 that might only accept positive values test the boundaries i.e. 0, 1, -1, Int32.MaxValue, Int32.MinValue Int32.MaxValue - 1 Int32.MinValue + 1, begin to think (as you appear to be doing) how to break it. IF you run into a failure condition later, add a unit test for that for example. If you are passing something that will be in a repo somewhere, also consider the limits of that - for example date min/max differs in sql vs C# and by date vs DateTime etc. BeginDate/EndDate - is it inclusive or not etc.
Now each of those "FAILURE" points should do something, how is this handled by the callers/API code? How does it respond if an error is thrown?

Implementing a Simple Repository, Unit of Work with Dependency Injection

I have been trying to create a Repository Pattern along with Dependency injection, But Looks like I am missing some simple step. Here is my code
public class HomeController
{
private readonly ILoggingRepository _loggingRepository;
public HomeController(ILoggingRepository loggingRepository)
{
_loggingRepository = loggingRepository;
}
public void MyMethod()
{
string message = "MyMessage Called";
_loggingRepository .LogMessage(message);
}
}
// ILoggingRepository.cs
public interface ILoggingRepository
{
void LogMessage(string message);
}
// LoggingRepository.cs
public class LoggingRepository : ILoggingRepository
{
public void LogMessage(string message)
{
using (var dbContext = new DbContext())
{
var serviceLog = new Log() { Message = message, Logged = DateTime.UtcNow };
dbContext.Logs.Add(serviceLog);
dbContext.SaveChanges();
}
}
}
This works perfectly all right so far, but the problem arises when i make more than one repository calls.
Now I know that Entity framework 6.0 has inbuilt unit of work representation so I didn't created a UnitofWork Interface or class
But the problem appears when I do something like this in two different transactions. Lets say
Area area = _areaRepository.GetArea(); // Line 1
area.Name = "NewArea"; // Line 2
_areaRepository.SaveArea(area); // Line 3
now because it _areaRepository creates a new DbContext in Line 3, it doesn't changes the name of area as it doesn't consider EntityState.Modified
I have to explicitly set that, which isn't correct.
So I guess I need to do all this in single Transaction, Where I am doing wrong here ?
What is the correct and best way to achieve this, Should I inject my DbContext also into the repository?

This is how I doit all times:
If dont use Repository or Unit of Work layers, because Entity Framework db Context already implements those patterns. So, I only have a Service layer:
public interface IBaseService<VO, ENT>{
IQueryable<VO> GetAll();
VO Get(object id);
}
public abstract class BaseService<VO, ENT> : IBaseService<VO, ENT>{
MyContext db;
public BaseService(MyContext db){
this.db = db;
}
public IQueryable<VO> GetAll(){
return db.Set<ENT>().ProjectTo<VO>();
}
}
A service class have a dbContext injected in the constructor. This classes are located in a Service library. Then, how the dbContext and the service are resolved is a problem of the project who will be using them. The ProjectTo method is an extension for IQueryable from the Automapper Nuget. For example:
A Windows Service needs all services instance in the same thread shares the same dbContext. So, in the windows service project, I use Ninject https://www.nuget.org/packages/Ninject/4.0.0-beta-0134, this library is a dependency resolver, wich I use to configure how dependencies are builded, creating a Kernel, like this:
var kernel = new StandardKernel();
kernel.Bind<MyContext>().ToSelf().InThreadScope();
kernel.Bind<IServiceImplInterface>().To<ServiceImplClass>().InThreadScope();
I you are creating a Web project, you will need to install a aditional nuget (Ninject.WebCommon, Ninject.Web.COmmon.WebHost, Ninject.MVC5) to provide a .InRequestScope() method to the binding configuration, like this:
var kernel = new StandardKernel();
kernel.Bind<MyContext>().ToSelf().InRequestScope();
kernel.Bind<IServiceImplInterface>().To<ServiceImplClass>().InRequestScope();
You need setup those kernel when the app startup. In a web project is in the global.asax, in a windows service project, should be in the Service constructor:
You can visit www.ninject.org/learn.html to learn more about ninject. But, there are othres like Autofac or Caste Windsor, it is up to you. If you like to keep using the repository pattern, just use Ninject inject them into the Service layer, like i did with the dbContext.

The best approach is to have one instance of DbContext, injecting it on each repository implementation. That way you will have a single instance of the database context, so EF will be able to detect changes on the entity objects.
If you need to use isolated dbContexts as in your example, then you need to explicitly set the state of the object as Modified.
Depending on the type of project, you should set the context on a specific scope. For example, for web applications one option is to use instance per Web request (per lifetime scope). Check this url where you can see a good explanation of the different instance scopes.
The using statement simply creates a new scope, executing the Dispose() method after the code block. EF does a lot on the background to maintain the UoW and state of the objects, but in your case, with the using, you are not using this fature.

First, a DbContext is a repository. If you want to wrap it in a custom repository, they should have the same lifecycle.
Second, your Unit-of-work is your controller. The repository should be scoped to unit-of-work.
This means that your repository needs to be Disposable, since the DbContext is.
So something like:
public interface ILoggingRepository : IDisposable
{
void LogMessage(string message);
}
// LoggingRepository.cs
public class LoggingRepository : ILoggingRepository
{
MyDbContext db;
public LoggingRepository(MyDbContext db)
{
this.db = db;
}
public void Dispose()
{
db.Dispose();
}
public void LogMessage(string message)
{
var serviceLog = new MonitoringServiceLog() { Message = message, Logged = DateTime.UtcNow };
db.MonitoringServiceLogs.Add(serviceLog);
db.SaveChanges();
}
}
If your ILoggingRepository wan't a database, it might be a file or something else that is expensive to create or open and needs to be closed.

ASP.Net MVC & Entity Framework project architecture WITHOUT repository pattern

I'm starting a new small project with ASP.NET MVC and Entity Framework. (SQL Server - around 20 DB tables)
In past projects I’ve used Linq2SQL but it seems to be obsolete.
I've read a lot of posts on using repository pattern for EF (pros and cons) , For me it seems better/simpler to code without repository pattern.
I created the following project architecture :
namespace MySite.Models
{
public class User
{
public Int32 ID { get; set; }
public String Email { get; set; }
public String Password { get; set; }
public String Name { get; set; }
public Int32 Gender { get; set; }
}
}
namespace MySite.DAL
{
public class Users
{
public static IEnumerable<User> GetUsers()
{
using (var context = new DatingSiteContext())
{
return context.Users.ToList();
}
}
public static User GetUserByID(int id)
{
using (var context = new DatingSiteContext())
{
return context.Users.Find(id);
}
}
}
namespace MySite.Controllers
{
public class HomeController : Controller
{
public ActionResult Index()
{
ViewBag.Message = "Modify this template to jump-start your ASP.NET MVC application.";
var users = DAL.Users.GetUsers();
return View(users);
}
}
}
What are the disadvantage of using EF like this? (Except lack of unit
testing support)
Is it wrong to create a new DbContext on each call to DAL ? Any Performance hit?
Any other recommended structure for using EF ? Examples? :)
Would you use Linq2SQL in a new project ?
Thank you.
Edit:
The code inside GetUsers() and GetUserByID() is just for example , i understand its a bad practice to return all records from the db (paging or filter in missing)

You actually just created a repository only you call it a 'data access layer' which is, in my opinion, not a good name since Entity Framework is the data access layer. A repository is an abstraction on top of a data access layer, Entity Framework in this case.
Is it wrong to create a new DbContext on each call to DAL ? Any
Performance hit?
Nope, it's just fine, but it might cause trouble when you fetch an entity in one instance of DbContext, and try to update it in another instance.
Would you use Linq2SQL in a new project ?
Nope, Microsoft proposed Entity Framework as the successor of L2SQL and active development of it has stopped.
Any other recommended structure for using EF ? Examples? :)
The approach you use, specific repositories, will result in a lot of redundant code. You could create a generic repository implementing an interface:
public interface IRepository<TEntity>
where TEntity : class, new()
{
IEnumerable<TEntity> GetAll();
TEntity GetById(int id);
IQueryable<TEntity> Table { get; }
}
And an implementation of this:
public EfRepository<TEntity> : IRepository<TEntity>
where TEntity : class, new()
{
private readonly DatingSiteContext _context;
public EfRepository()
{
_context = new DatingSiteContext();
}
private IDbSet<TEntity> Entities
{
get
{
return _context.Set<TEntity>();
}
}
public IEnumerable<TEntity> GetAll()
{
return Entities.ToList();
}
public TEntity GetById(int id)
{
return Entities.Find(id);
}
public IQueryable<TEntity> Table
{
get { return Entities; }
}
}
You can use this repository in your controller like this:
public class HomeController : Controller
{
private readonly IRepository<User> _userRepository;
public HomeController()
{
_userRepository = new EfRepository<User>();
}
public ActionResult Index()
{
var users = _userRepository.GetAll();
var inactiveUsers = _userRepository.Table.Where(u => !u.Active).ToList();
}
}
This generic repository allows you to create mocked repositories:
public class FakeUserRepository : IRepository<User>
{
// ...
}
This approach might seem like a lot of code, but as your entity type amount grows, it will save you a lot of work since all you have to do is create an IRepository<> field in a controller. Yet you have a lot of flexibility with the IQueryable<> property which allows deferred execution.
I'm not saying this is the best method, just one I use regularly in projects. I have to say that I usually write a business (service) layer between the controller and the repositories. I keep my business logic and complex Linq queries (and their execution) there. I also use an IoC container which handles the lifetime of my objects (instances of DbContext and services for example). See this question for more information about that.

My thoughts
Whats the disadvantages:
You cant really unit test anywhere that uses the static methods you have defined in your DAL.
They are also strongly coupled making them more difficult to swap out at runtime, if that became a requirement.
You may start to get additional complications if you need to commit several updates in a transaction
Is it wrong to create a new DbContext on each call?
No, this is fine. The DbContext is lightweight and meant to be used this way.
Other patterns
You already mentioned the repository pattern which is pretty solid, especially when used with a unit of work pattern.
Would you use Linqtosql
No - Linqtosql is pretty much done with, entity framework provides a more complete and generally better solution to this problem

I would rethink how you implemented GetUsers(). You are calling ToList() which will cause all the rows from the underlying table to be returned and stored in memory. If the tables grows large enough you will run into performance issues. It's better to return an IQueryable<User> instead and have your method return context.Users.
Of course you'll run into the problem that the context has already been disposed by the time you execute the IQueryable<>, so you'll need to handle the life cycle of the context in a different way.
If the project is small enough, then you can just store an instance of the Context at the Controller level, and dispose of it when the controller is being disposed. If you do that, make sure you don't do anything in your views that would cause additional queries to be executed (e.g. access a collection off of User if one exists) or else that will error out.