I've this interface:
public interface IRepository<T>
{
List<T> List();
T Get(int Id);
bool Add(T entity);
bool Update(T entity);
}
And I've this class:
public class Customer<T> : IRepository<Entities.Customer>
{
public Entities.Customer Get(int Id)
{
var c = new Entities.Customer();
return c;
}
//continue...
}
How can I cast a generic class to a generic interface like so:
//Other method
public IRepositorio<T> DoStuff<T>(int Id)
{
var a = (IRepository<Entities.Customer>)Activator.CreateInstance(typeof(T)); // ok
var b = (IRepository<T>)Activator.CreateInstance(typeof(T)); // Exception: unable to cast
return object; // an object
}
And I call from this MCV controller:
public ActionResult Home()
{
var repo = new Repository();
repo.DoStuff<Customer<Entities.Custormer>>(10);
return View();
}
My conception is ok? This is possible without dynamic?
Based on the code supplied, I've tried the following which compiles OK
public class Entities {
public class Customer {
}
}
public interface IRepository<T> {
T Get(int Id);
}
public class Customer<T> : IRepository<Entities.Customer> {
public Entities.Customer Get(int Id) {
var cliente = new Entities.Customer();
return cliente;
}
}
public class foo {
public static IRepository<T> DoStuff<T>(int Id) {
var a = (IRepository<Entities.Customer>)Activator.CreateInstance(typeof(T));
var b = (IRepository<T>)Activator.CreateInstance(typeof(T));
return b; // an object
}
}
However, I'm not sure what T is meant to be. When I run and call
foo.DoStuff<Entities.Customer>(0);
then I get a runtime error on the var a line, because the class Entities.Customer does not implement the interface IRepository<T>. If I call
foo.DoStuff<Customer<Entities.Customer>>(0);
then I get the runtime error on the 'var b' line, because the class Customer<Entities.Customer> implements IRepository<Entities.Customer> and not IRepository<Customer<Entities.Customer>>
Both exceptions are correct, so hopefully the author of the question can work out where the problem lies from this answer.
Activator.CreateInstance(typeof(T)); - this creates for you new instance of T, which is Entities.Customer in your example, but it looks like you want to create instance of Customer<Entities.Customer>.
Related
I want to pass Dbset Object to my method.
This is my Method:
public static class MyClass
{
public static Floor ReturnObject(this DbSet<Floor> floor, int Id)
{
var context = floor.passContext() as MyDBContext;
var data = context.floors.Where(a =>a.Id == Id).FirstOrDefault();
return ad;
}
}
public class MyDBContext: DbContext
{
public DbSet<Floor> floors { get; set; }
}
public static DbContext passContext<TEntity>(this DbSet<TEntity> dbSet)
where TEntity : class
{
//code....
}
Now i want to use my method of static class MyClass that is ReturnObject.
I want to use ReturnObject method in my Controller.
I know i can declare it as private member like this in my controller:
This is my controller:
public class MyController
{
private DbSet<Floor> floor;//but is this a good way???
public ActionResult Index(int Id)
{
var data=MyClass.ReturnObject(????,Id)//what should come in place of question mark??
}
}
How should i pass my First Parameter to ReturnObject Method???
Change your ReturnObject method. It should only take Id as parameter and filter data than return object of Floor.
public static Floor ReturnObject(int Id)
{
using(MyDBContext context = new MyDBContext())
{
var data = context.floors.Where(a =>a.Id == Id).FirstOrDefault();
return ad;
}
}
And when you call it than only pass id as paramter
var data=MyClass.ReturnObject(Id);
This will return object of floor which will be stored in data.
I am trying to learn the repository pattern and looking at a generic repository I cannot see how to handle customized select statements. For example, using this article the author uses a select by ID and a select all.
public interface IGenericRepository<T> where T:class
{
IEnumerable<T> SelectAll();
T SelectByID(object id);
void Insert(T obj);
void Update(T obj);
void Delete(object id);
void Save();
}
Later the article the IGenericRepository interface is implemented using Northwind. Then that is used to create a Customer controller.
public class CustomerController : Controller
{
private IGenericRepository<Customer> repository = null;
public CustomerController()
{
this.repository = new GenericRepository<Customer>();
}
...
This would handle selecting a list of all Customers or for one Customer by ID but where I get stuck is some more real world examples like "select all Customers for a client" or "select all Customers for a region". Plus, you could have another controller based on a different entity that would filter on different attributes. I assume I'm missing something basic. If the user interface needed to present the Customer entity (or any other entity) by various filters, how would this be done by sticking with one generic repository?
Here you go; to handle any select criteria apart from the Id, you can add Where method
like below
public interface IGenericRepository<T> where T:class
{
IEnumerable<T> SelectAll();
T SelectByID(object id);
IEnumerable<T> Where(Expression<Func<T,bool>> predicate)// this one
void Insert(T obj);
void Update(T obj);
void Delete(object id);
void Save();
}
Now in the Where method implementation do it like this
public IEnumerable<T> Where(Expression<Func<T,bool>> predicate)
{
return _objectSet.Where(predicate).AsEnumerable();
}
Here _objectSet in created in repository constructor like this :
public Repository(ObjectContext context)
{
_context = context;
_objectSet = _context.CreateObjectSet<T>();
}
public CustomerController()
{
_context = new NorthwindEntities();
_reporsitory = new Repository<Customer>(_context);
}
Use of Where method like
reporsitory.Where(c=>c.Country=="Canada").ToList();
For full reference see this project on codeplex (download /browse source code)
https://efgenericrepository.codeplex.com/SourceControl/latest
I think the implementation of the GenericRepository should somehow be able to return the IQueryable of current entity, like adding Get() method.
protected IQueryable<T> Get() // Notice that the access modifier is protected.
{
return table;
}
Then you could just create a derived class from GenericRepository and add a select method that accepts the Filter class.
public class CustomerRepository : GenericRepository<Customer>
{
public IEnumerable<T> SelectAll(CustomerFilter filter){ .. }
}
The filter class contains 2 filters.
public class CustomerFilter
{
public int? ClientId { get; set; }
public int? RegionId { get; set; }
}
Then the SelectAll implementation would be.
public IEnumerable<T> SelectAll(CustomerFilter filter)
{
var query = Get();
if (filter == null)
{
return query;
}
if (filter.ClientId.HasValue)
{
query = query.Where(q => q.ClientId == filter.ClientId.Value);
}
if (filter.RegionId.HasValue)
{
query = query.Where(q => q.RegionId == filter.RegionId.Value);
}
return query;
}
In the controller, calling it like.
public ActionResult Get(int? clientId, int? regionId)
{
var filter = new CustomerFilter { ClientId = clientId, RegionId = regionId };
var customers = _repository.SelectAll(filter);
return View();
}
You might need to see this post as your reference.
An approach I've seen in one asp.net mvc based mission critical app, is to use the generic interface as defined in the question. Then there is an abstract class that implements that interface. And there is one more repository class that inherits the abstract class, which has all methods specific to that class.
public interface IGenericRepository<T> where T:class
{
...
}
public abstract class GenericRepository<T> : IGenericRepository where T:class
{
...
}
And the CustomerRepository class
public class CustomerRepository : GenericRepository<Customer>
{
//add method specific to Customer like select Customers in specific country
}
And in the controller
public class CustomerController : Controller
{
private CustomerRepository repository = null;
public CustomerController()
{
this.repository = new CustomerRepository();
}
...
My DbContext implementation implements two interfaces.
I'm trying to follow best practices and instantiate one DbContext instance per HTTP request.
However, I have a controller action where I need to instantiate two classes, each of which takes different interface in constructor.
I am worried if in that scenario, for that specific action, two DbContext instances would be raised.
I've setup my ContainerBuilder like this:
builder.RegisterType<MyDbContext>()
.As<IWorkflowPersistenceStore>()
.As<IDocumentPersistenceStore>()
.InstancePerHttpRequest();
builder.RegisterType<WorkflowManager>().As<IWorkflowManager>().InstancePerHttpRequest();
builder.RegisterType<DocumentManager>().As<IDocumentManager>().InstancePerHttpRequest();
public class OperationController : Controller
{
private IWorkflowManager _workflowManager;
private IDocumentManager _documentManager;
public OperationController(IWorkflowManager workflowManager, IDocumentManager documentManager)
{
_workflowManager = workflowManager;
_documentManager = documentManager;
}
public ActionResult SaveWorkflowDocument(...)
{
// will my managers point to same DbContext?
_workflowManager.DoSomething(...);
_documentManager.DoSomethingElse(...);
return View();
}
}
public class WorkflowManager : IWorkflowManager
{
private IWorkflowPersistenceStore _store;
public WorkflowManager(IWorkflowPersistenceStore store)
{
_store = store;
}
}
public class DocumentManager : IDocumentManager
{
private IDocumentPersistenceStore _store;
public DocumentManager (IDocumentPersistenceStore store)
{
_store = store;
}
}
Is this good enough?
Do I have to add .SingleInstance()? I'm worried that it might create singleton for whole application.
I think you're ok with what you have. Test passes:
using Autofac;
using NUnit.Framework;
namespace AutofacTest
{
[TestFixture]
public class ScopeTest
{
[Test]
public void Test()
{
var builder = new ContainerBuilder();
builder.RegisterType<Component>()
.As<IServiceA>()
.As<IServiceB>()
.InstancePerLifetimeScope();
using (var container = builder.Build())
using (var scope = container.BeginLifetimeScope())
{
var a = scope.Resolve<IServiceA>();
var b = scope.Resolve<IServiceB>();
Assert.AreEqual(a, b);
}
}
}
public interface IServiceA { }
public interface IServiceB { }
public class Component : IServiceA, IServiceB { }
}
I am learning how to use nInject for a new application I am developing, and I have created the following sample code that can be copied/pasted into a simple console app. It successfully returns an instance of IFoo, but I have a question about it.
How would I modify the code to have the FooManager class create an instance of the Foo object without doing a 'new'. Does the kernal have to be injected as well? But if the kernal is injected and I change the line to read var foo = _kernel.Get<IFoo>(), isn't that introducing a service locator anti-pattern?
namespace IOCTest
{
class Program
{
static void Main(string[] args)
{
using (IKernel kernel = new StandardKernel(new StandardModule()))
{
// do something with the kernal
var mgr = kernel.Get<IFooManager>();
var foo = mgr.GetById(1);
}
}
}
public class StandardModule : Ninject.Modules.NinjectModule
{
public override void Load()
{
Bind<IDatabase>()
.To<Database>()
.InTransientScope();
Bind<IFooManager>()
.To<FooManager>()
.InTransientScope();
}
}
//******************************************************
public interface IDatabase
{
object[] GetScalar(int id);
}
public class Database : IDatabase
{
public object[] GetScalar(int id)
{
return new object[] { "RowName" };
}
}
//******************************************************
public interface IFooManager
{
IFoo GetById(int id);
}
public class FooManager : IFooManager
{
private IDatabase _db;
public FooManager(IDatabase db) { _db = db; }
public IFoo GetById(int id)
{
var results = _db.GetScalar(id);
var foo = new Foo(); // <-- HOW DO I ELIMINATE THIS DEPENDENCY?
foo.Name = results[0].ToString();
return foo;
}
}
//******************************************************
public interface IFoo
{
string Name { get; set; }
}
public class Foo : IFoo
{
public string Name { get; set; }
}
//******************************************************
}
First you have to think about the purpose of Foo. Is this some kind of a datacontainer or some service?
In the first case your code is perfect like it is. Datacontainers have no dependencies and shouldn't be created by the IoC container.
In the second case read about Ninject.Extensions.Factory.
http://www.planetgeek.ch/2011/12/31/ninject-extensions-factory-introduction/
https://github.com/ninject/ninject.extensions.factory/wiki
There are a couple ways to eliminate that dependency. You could do the same thing you did with the Database dependency and use constructor injection. You could do property injection (https://github.com/ninject/ninject/wiki/Injection-Patterns). Another way, and perhaps what you are looking for, would be service location. To do that you can update your FooManager ctor to require an IKernel. This will be resolved automatically and you can then use the kernel that is passed in to get Foo.
public class FooManager : IFooManager
{
private IDatabase _db;
private IKernel _kernel;
public FooManager(IDatabase db, IKernel kernel) { _db = db; _kernel = kernel;}
public IFoo GetById(int id)
{
var results = _db.GetScalar(id);
// var foo = new Foo(); // <-- HOW DO I ELIMINATE THIS DEPENDENCY?
var foo = kernel.Get<IFoo>(); // Like this perhaps
foo.Name = results[0].ToString();
return foo;
}
}
I have successfully setup a simple mvc application that lists teams. I'm using Ninject to inject the appropriate repository depending on the controller (thanks to stack overflow ;). All looks good, except that the repository code looks exactly the same. And I know that's wrong. So my TeamRepository has two classes (for now).
public class SwimTeamRepository : ITeamRepository<SwimTeam>
{
private readonly Table<SwimTeam> _teamTable;
public SwimTeamRepository(string connectionString)
{
_teamTable = (new DataContext(connectionString).GetTable<SwimTeam>());
}
public IQueryable<SwimTeam> Team
{
get { return _teamTable; }
}
}
public class SoccerTeamRepository : ITeamRepository<SoccerTeam>
{
private readonly Table<SoccerTeam> _teamTable;
public SoccerTeamRepository(string connectionString)
{
_teamTable = (new DataContext(connectionString).GetTable<SoccerTeam>());
}
public IQueryable<SoccerTeam> Team
{
get { return _teamTable; }
}
}
They look exactly the same except for the Class and Table name, so clearly I need to re-factor this. What would be the best approach here? Singleton? Factory Method?
Thanks in advance!
You could use generics:
public interface ITeamRepository<T>
{
}
public class TeamRepository<TTeam> : ITeamRepository<TTeam>
where TTeam : Team
{
private readonly Table<TTeam> _teamTable;
public TeamRepository(string connectionString)
{
_teamTable = (new DataContext(connectionString).GetTable<TTeam>());
}
public IQueryable<TTeam> Team
{
get { return _teamTable; }
}
}
public class Team
{
}
public class SwimTeam : Team
{
}
Then use it like so...
public void MyMethod()
{
var repository = new TeamRepository<SwimTeam>();
}
...and set up your IoC container w/ Ninject like so...
public class MyModule : NinjectModule
{
public override void Load()
{
Bind<ITeamRepository<SwimTeam>>
.To<TeamRepository<SwimTeam>>();
}
}
public void MyMethod()
{
var repository = kernel.Get<ITeamRepository<SwimTeam>>();
}
If you want to get REAL generic and have a single repository for ALL of your mapped classes, you can do something like this:
public interface IRepository
{
IQueryable<T> Get<T>() where T : class, new();
}
public class Repository : IRepository, IDisposable
{
private DataContext _dataContext;
public Repository(string connectionString)
{
_dataContext = new DataContext(connectionString);
}
public IQueryable<T> Get<T>()
where T : class, new()
{
return _dataContext.GetTable<T>().AsQueryable();
}
public void Dispose()
{
if (_dataContext != null)
{
_dataContext.Dispose();
_dataContext = null;
}
}
}
...which you could call like so (after setting up your Ninject container)...
using (var repository = kernel.Get<IRepository>())
{
var swimTeam = repository.Get<SwimTeam>();
}
Since Ninject takes care of the life-cycle management of your objects, you don't HAVE to wrap the repository in a using statement. In fact, you don't want to use a using statement there at all if you plan to use the repository more than once within the scope of its lifetime. Ninject will automatically dispose of it when it's life-cycle ends.
Here's a good article by Rob Conery on using this kind of technique to reduce the friction of using different ORMs.
EDIT by keeg:
I Think
public class TeamRepository<TTeam> : ITeamRepository<TTeam> where TTeam : Team {}
Should be
public class TeamRepository<TTeam> : ITeamRepository<TTeam> where TTeam : class {}
Please correct if I'm wrong.
Is this what you want?
public class TeamRepository : ITeamRepository<T>
{
private readonly Table<T> _teamTable;
public TeamRepository(string connectionString)
{
_teamTable = (new DataContext(connectionString).GetTable<T>());
}
public IQueryable<T> Team
{
get { return _teamTable; }
}
}