I am trying to implement MEF framework in my .Net core and .Net framework application. Here is my sample.
Project One class library:
[Export(typeof(IProductRepository))]
public class ProductRepository : IProductRepository
{
public ProductRepository(ApplicationDBContext context)
{
this.context = context;
}
}
Project Two class library:
[Export(typeof(IProductService))]
public class ProductService : IProductService
{
public ProductService(IProductRepository _ProductRepository)
{
}
}
So here both project depends on interface injection on constructor, and in another class library i am implementing the MEF like
[System.Composition.ImportMany]
public static IProductService ProductService{ get; set; }
[System.Composition.ImportMany]
public static IProductRepository ProductRepository{ get; set; }
var executableLocation = Assembly.GetEntryAssembly().Location;
var assemblies = Directory
.GetFiles(executableLocation , "*.dll", SearchOption.TopDirectoryOnly)
.Select(AssemblyLoadContext.Default.LoadFromAssemblyPath)
.ToList();
var configuration = new ContainerConfiguration().WithAssemblies(assemblies);
using (var container = configuration.CreateContainer())
{
ProductRepository= container.GetExport<IProductRepository>();
ProductService= container.GetExport<IProductService>();
}
Here I am getting error 'No export was found for the contract 'IProductRepository"IProductService"'
My question is,
how to pass an interface to constructor of class using MEF framework?
how to pass an object to constructor of class using MEF framework?
How to implement MEF when multiple projects are involved?
After searching I have found the answer it will goes as,
The repository code should be like below
[Export(typeof(IProductRepository))]
public class ProductRepository : IProductRepository
{
[ImportingConstructor]
public ProductRepository(ApplicationDBContext context)
{
this.context = context;
}
}
The service code should be like below
[Export(typeof(IProductService))]
public class ProductService : IProductService
{
[Import(typeof(IProductRepository ))]
private IProductRepository productRepository;
[ImportingConstructor]
public ProductService(IProductRepository _ProductRepository)
{
}
}
And using System.ComponentModel.Composition DLL implement the MEF container part as below
[Import(typeof(IProductService))]
public static IProductService ProductService { get; set; }
[Import(typeof(IProductRepository))]
public static IProductRepository ProductRepository { get; set; }
var catalog = new DirectoryCatalog(GlobalVariables.ApplicationAssemblyPath, "*.dll");
container = new CompositionContainer(catalog);
ProductRepository = container.GetExportedValue<IProductRepository>();
ProductService = container.GetExportedValue<IProductService>();
Hence from the ProductRepository, ProductService we will get the instance
Related
I want to get value of appsetting inside StartUp and also using services for saving them.
I create a static IServiceCollection method for AddTransient my custom service.
I define a readonly variable for keep the appsetting values. My problem is that, this service creates new instance for readonly variable, for all calling.how can I prevent this?
and I have a question that other extensions like AddOpenIdConnect, how to work with their configs, I mean how to save and use them?
this is startup:
public void ConfigureServices(IServiceCollection services){
...
services.AddMyIntegration(conf =>
{
conf.ConnectionString = Configuration.GetConnectionString("Integration");
conf.AgentApiAddress = Configuration["AgentApiAddress"];
});
}
....
public static class MyExtension
{
public static IServiceCollection AddMyIntegration(this IServiceCollection services, Action<MyConstantsProvider> myConstantsProvider)
{
services.AddTransient((t) =>
{
return new MyService(myConstantsProvider);
});
return services;
}
}
this is my service:
public class MyService
{
public readonly MyConstantsProvider Provider;
public MyService(Action<MyConstantsProvider> configure)
{
Provider = new MyConstantsProvider();
configure(Provider);
}
}
public class MyConstantsProvider
{
public string ConnectionString { get; set; }
public string AgentApiAddress { get; set; }
}
Update my question:
Finally I fixed my issue by add MyConstantsProvider as singletone instead of MyService so this creates new instance of variable at the first time in extension class:
public static class MyExtension
{
public static IServiceCollection AddMyIntegration(this IServiceCollection services, Action<MyConstantsProvider> myConstantsProvider)
{
var provider = new MyConstantsProvider();
myConstantsProvider(provider);
services.AddSingleton(provider);
services.AddTransient<MyService>();
return services;
}
}
this is MyService class:
public class MyService
{
public readonly MyConstantsProvider Provider;
public MyService(MyConstantsProvider provider)
{
Provider = provider;
}
}
I wonder why we make it so complicated ? I just saw we're trying to read appsettings later in the application somewhere, and for this, the framework have default implementation to back us up.
Our app settings might look like
{
"Catalog": {
"ConnectionString": "SomeConnection",
"AgentApiAddress": "http://somewhere.dev"
}
}
Then our class could be
public class MySetting
{
public string ConnectionString { get; set; }
public string AgentApiAddress{ get; set; }
}
Config register it in startup (or somewhere we like in .net 6)
services.Configure<MySetting>(configuration.GetSection("Catalog"));
Retrive it later in the app via DI
public class SomeService
{
private readonly MySetting _setting;
public SomeService(IOptions<MySetting> config)
{
_setting = config.Value;
}
}
For setting that can be change dynamically, take a look at IOptionsMonitor
Or that might be some special case that I miss ?
I'm trying to configure an API which a controller use depency injection to inject an object to this controller
public class BaseAPIController
{
private readonly Repository _repository;
public BaseAPIController(Repository repository)
{
_repository = repository;
}
// some common functions and properties are declared here
}
public class AccountController : BaseAPIController
{
public AccountController(Repository repository) : base(repository)
{ }
}
but it throws an exception that tells "Some services are not able to be constructed..."
I tried a solution that use ILogger<Repository> instead of using Repository instance then this runs properly
public class AccountController : BaseAPIController
{
public AccountController(ILogger<Repository> repository) : base(repository)
{ }
}
the registion service in startup.cs code
public void ConfigureServices(IServiceCollection services)
{
services.AddControllers();
services.AddScoped<IRepository, Repository>();
services.AddSingleton<WeatherForecastController, WeatherForecastController>();
}
and the declaration of Repository class
public interface IRepository
{
void DoSomething1();
void DoSomething2();
void DoSomething3();
}
public class Repository : IRepository
{
public readonly string _connectionString;
public Repository(string connectionString)
{
_connectionString = connectionString;
}
public void DoSomething1() {}
public void DoSomething2() {}
public void DoSomething3() {}
}
How can I archive the configuration above without using ILogger instance
Thanks
This is the registration you made:
services.AddScoped<IRepository, Repository>();
But this is AccountController's constructor:
AccountController(Repository repository)
Notice how AccountController is depending on the concrete type Repository; not on the IRepository interface. Because of this registration, Repository can only be resolved through its IRepository interface, but not directly (that's by MS.DI's design).
The solution, therefore, is to change AccountController's constructor to the following:
AccountController(IRepository repository)
The issue is that DI cannot create an instance of Repository because there is no parameterless constructor. Take a look at the docs for injecting settings rather than requiring a string in the constructor. Add your connection string to your appsettings.json file:
{
"AppSettings": {
"ConnectionString": "<connection_string>"
}
}
In ConfigureServices register your settings class:
public class AppSettings
{
public string ConnectionString;
}
public void ConfigureServices(IServiceCollection services)
{
services.Configure<AppSettings>(Configuration.GetSection(AppSettings));
...
}
Then your Repository class constructor would look like this:
public Repository(IOptions<PositionOptions> options)
{
_connectionString = options.Value.ConnectionString;
}
You also need to inject the interface IRepository, not the concrete class into your controller.
public class BaseAPIController
{
private readonly IRepository _repository;
public BaseAPIController(IRepository repository)
{
_repository = repository;
}
// some common functions and properties are declared here
}
I am getting the following error whenever I try to inject one of my service's dependency into the MVC controller:
Error activating IFeedService No matching bindings are available, and the type is not self-bindable.
Activation path:
2) Injection of dependency IFeedService into parameter svc of constructor of type FeedController
1) Request for FeedController
Suggestions:
1) Ensure that you have defined a binding for IFeedService.
2) If the binding was defined in a module, ensure that the module has been loaded into the kernel.
3) Ensure you have not accidentally created more than one kernel.
4) If you are using constructor arguments, ensure that the parameter name matches the constructors parameter name.
5) If you are using automatic module loading, ensure the search path and filters are correct.
======================================================================
Here's how my code looks like:
ObjectFactory.cs
private static void RegisterServices(IKernel kernel)
{
// Contexts
kernel.Bind<IEntityObjectContext>().To<Entities>();
kernel.Bind<IAzureObjectContext>().To<AzureTableObjectContext>();
// Repositories
kernel.Bind<IEFRepository>().To<EFRepository>();
kernel.Bind<IAzureRepository>().To<AzureRepository>();
// Services
kernel.Bind<IFeedService>().To<FeedService>();
}
IEFRepository.cs
public interface IEFRepository : IDisposable
{
void SetContext(IEntityObjectContext context);
IQueryable<T> GetAll<T>() where T : class;
}
EFRepository.cs
public class EFRepository : IEFRepository
{
internal IEntityObjectContext context;
private Dictionary<Type, object> objectSets;
public EFRepository(IEntityObjectContext context)
{
this.context = context;
objectSets = new Dictionary<Type, object>();
}
public void SetContext(IEntityObjectContext context)
{
this.context = context;
}
}
IFeedService.cs
public interface IFeedService : IDisposable
{
IQueryable<FeedItem> GetPosts();
}
FeedService.cs
public class FeedService : IFeedService
{
private IEntityObjectContext _context;
private readonly IEFRepository _repo;
public FeedService(IEntityObjectContext context,
IEFRepository repo)
{
_context = context;
_repo = repo;
_repo.SetContext(_context);
}
public IQueryable<FeedItem> GetPosts()
{
using (_repo)
{
return _repo.GetAll<FeedItem>().Take(10);
}
}
}
FeedController.cs
public class FeedController : Controller
{
private readonly IFeedService _svc;
public FeedController(IFeedService svc)
{
_svc = svc;
}
}
As you can see, there are some nested dependency there in action. Not sure though, what needs to be added/removed for this bit to work.
Note: The error is thrown whenever I request the Feed/FetchFeed path. I also tried to comment out the FeedService's constructor portion to see if the nested dependencies are creating any problem, but again same error was thrown.
EDIT 1:
Rest of the code for the ObjectFactory.cs
class ObjectFactory
{
static ObjectFactory()
{
RegisterServices(kernel);
}
static IKernel kernel = new StandardKernel();
public static T GetInstance<T>()
{
return kernel.Get<T>();
}
private static void RegisterServices(IKernel kernel)
{
//...
}
}
EDIT 2:
I even tried to write a fairly basic service, but still the same error. Here's what I tried with:
public interface ITest
{
void CheckItOut();
}
public class Test : ITest
{
public void CheckItOut()
{
}
}
ObjectFactory.cs
kernel.Bind<ITest>().To<Test>();
A bit of history first. I created a EF Code First Library that contains POCO Objects as my Models, a generic DataProvider that inherits from DbContext, generic Repostory that implements the generic DataProvider, and a generic Service that implements the repository. I have used this library successfully in WPF (MVVM), ASP.Net, Window Forms, and ASP MVC applications.
For this discussion I will reference the Company Model
From the top down, I create a Service class called CompanyService that inherits from a base Service Class. The CompanyService class contains all of the business logic for the Company Model. This class uses the Repository class to perform the CRUD operations. The Repository then encapsulates all the DataProvider class operations.
I have done some research on using EF with WCFDataService, but I can't get my head around how to implement my library with it, particulary when it comes to overriding the CreateDataSource() Method.
It may be that I should just use a WCF Service instead, maybe I'm not understanding the purpose of the WCFDataService.
I have listed partial code for the classes involved:
public class CompanyService : ServiceBase<Company> ,ICompanyService
{
public Company GetCompanyByFolderId(string eFolderId)
{
return (Company)GetModelByFolderId(eFolderId);
}
}
public abstract class ServiceBase<TModel> : IService<TModel> where TModel : class, IModel
{
private IDataProvider _dataProvider;
public IDataProvider DataProvider
{
get
{
if (_dataProvider == null)
{
string connectionStringName = Properties.Settings.Default.DataProvider;
bool enableLazyLoading = true;
_dataProvider = new DataProvider(connectionStringName, enableLazyLoading);
}
return _dataProvider;
}
set
{
_dataProvider = value;
}
}
private IRepository<TModel> _repository;
public IRepository<TModel> Repository
{
get
{
if (_repository == null)
{
_repository = new Repository<TModel>(DataProvider);
}
return _repository;
}
set
{
_repository = value;
}
}
public TModel GetModelByFolderId(String folderId)
{
return GetTable().FirstOrDefault(o => o.EFolderid == folderId);
}
public virtual IQueryable<TModel> GetTable()
{
return Repository.GetTable();
}
}
public class Repository<TModel> : IRepository<TModel> where TModel : class, IModel
{
private IDataProvider _dataProvider;
public Repository(IDataProvider dataProvider)
{
_dataProvider = dataProvider;
}
private IDbSet<TModel> DbSet
{
get
{
return _dataProvider.Set<TModel>();
}
}
public IQueryable<TModel> GetTable()
{
return _dataProvider.GetTable<TModel>();
}
}
public class DataProvider : DbContext, IDataProvider
{
public DataProvider()
{
}
public DataProvider(string connectionStringName, bool enableLazyLoading = true)
: base(connectionStringName)
{
Configuration.LazyLoadingEnabled = enableLazyLoading;
//Configuration.ProxyCreationEnabled = false;
}
public new IDbSet<TModel> Set<TModel>() where TModel : class
{
return base.Set<TModel>();
}
protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
modelBuilder.Configurations.Add(new CompanyMapping());
base.OnModelCreating(modelBuilder);
}
public IQueryable<TModel> GetTable<TModel>() where TModel : class
{
return Set<TModel>().AsQueryable();
}
}
Then my Test looks something like this:
[TestClass()]
public class CompanyServiceTest
{
[TestMethod()]
public void GetCompanies()
{
CompanyService target = new CompanyService();
IQueryable<Company> companies = target.GetTable();
Assert.IsNotNull(companies);
}
[TestMethod()]
public void GetCompanyByFolderId()
{
CompanyService target = new CompanyService();
Company company = target.GetCompanyByFolderId("0000000000000000000000000172403");
Assert.IsNotNull(company);
}
}
I'm using ASP.NET MVC 4 with Entity Framework 5. I have model classes and Entity Maps to map existing tables to those model classes. All this is setup fine and works great.
Now I want to mock this. I created Unit Of Work that takes the DataContext and uses a Generic Repository. Upon that I built services to be able to get data from many repositories at once and only needing to have one instance of the DataContext. This also works great.
Now to the problem: I want to test the services, with mock data. When I create the Unit Of Work instance, I want to be able to insert a DataContext that is mocked instead of the real DataContext.
I tried to create a IContext interface and let the real and mocked DataContext implement that but ran into problems with DbSet. I tried to use IDbSet and creating a FakeDbSet but without success. I also read on the internet that mocking the context with IDbSet and using a FakeDbSet is a bad approach.
Do you have any idea what would be the best way to achieve this? What I have now is the behavior I would like to keep, but would really like to be able to mock the data from the Model classes in the DataContext.
I'm aware of that Entity Framework already comes with Unit Of Work behavior and that you don't need to add extra behavior on top of that. But I wanted to wrap that inside of another class that keeps track of all the repositories (called UnitOfWork class).
Edit: I wrote two articles explaining my solution with both LINQ and Entity Framework.
http://gaui.is/how-to-mock-the-datacontext-linq/
http://gaui.is/how-to-mock-the-datacontext-entity-framework/
Here's my code:
IRepository.cs
public interface IRepository<T> where T : class
{
void Add(T entity);
void Delete(T entity);
void Update(T entity);
T GetById(long Id);
IEnumerable<T> All();
IEnumerable<T> Find(Expression<Func<T, bool>> predicate);
}
IUnitOfWork.cs
public interface IUnitOfWork : IDisposable
{
IRepository<TEntity> GetRepository<TEntity>() where TEntity : class;
void Save();
}
Repository.cs
public class Repository<T> : IRepository<T> where T : class
{
private readonly IDbContext _context;
private readonly IDbSet<T> _dbset;
public Repository(IDbContext context)
{
_context = context;
_dbset = context.Set<T>();
}
public virtual void Add(T entity)
{
_dbset.Add(entity);
}
public virtual void Delete(T entity)
{
var entry = _context.Entry(entity);
entry.State = System.Data.EntityState.Deleted;
}
public virtual void Update(T entity)
{
var entry = _context.Entry(entity);
_dbset.Attach(entity);
entry.State = System.Data.EntityState.Modified;
}
public virtual T GetById(long id)
{
return _dbset.Find(id);
}
public virtual IEnumerable<T> All()
{
return _dbset;
}
public IEnumerable<T> Find(Expression<Func<T, bool>> predicate)
{
return _dbset.Where(predicate);
}
}
UnitOfWork.cs
public class UnitOfWork<TContext> : IUnitOfWork where TContext : IDbContext, new()
{
private readonly IDbContext _ctx;
private Dictionary<Type, object> _repositories;
private bool _disposed;
public UnitOfWork()
{
_ctx = new TContext();
_repositories = new Dictionary<Type, object>();
_disposed = false;
}
public IRepository<TEntity> GetRepository<TEntity>() where TEntity : class
{
if (_repositories.Keys.Contains(typeof(TEntity)))
return _repositories[typeof(TEntity)] as IRepository<TEntity>;
var repository = new Repository<TEntity>(_ctx);
_repositories.Add(typeof(TEntity), repository);
return repository;
}
public void Save()
{
_ctx.SaveChanges();
}
public void Dispose()
{
Dispose(true);
GC.SuppressFinalize(this);
}
protected virtual void Dispose(bool disposing)
{
if (!this._disposed)
{
if (disposing)
{
_ctx.Dispose();
}
this._disposed = true;
}
}
}
ExampleService.cs
public class ExampleService
{
private IRepository<Example> m_repo;
public ExampleService(IUnitOfWork uow)
{
m_repo = uow.GetRepository<Example>();
}
public void Add(Example Example)
{
m_repo.Add(Example);
}
public IEnumerable<Example> getAll()
{
return m_repo.All();
}
}
ExampleController.cs
public IEnumerable<Example> GetAll()
{
// Create Unit Of Work object
IUnitOfWork uow = new UnitOfWork<AppDataContext>();
// Create Service with Unit Of Work attached to the DataContext
ExampleService service = new ExampleService(uow);
return service.getAll();
}
Your ExampleService class is expecting IUnitOfWork, that means you just need another IUnitOfWork that is a Mock and its GetRepository() method will return an IRepository Mock.
For example (not really a Mock but In-Memory stub):
public InMemoryRepository<T> : IRepository<T> where T : class
{
........
}
public InMemoryUnitOfWork : IUnitOfWork
{
public IRepository<TEntity> GetRepository<TEntity>() where TEntity : class
{
return new InMemoryRepository<TEntity>();
}
}
Then:
public IEnumerable<Example> GetAll()
{
// Create Unit Of Work object
IUnitOfWork uow = new InMemoryUnitOfWork();
// Create Service with Unit Of Work
ExampleService service = new ExampleService(uow);
return service.getAll();
}
You can follow the following link it is very helpful.
Generic Repository Pattern in MVC3 Application with Entity Framework
Entity Framework and Data Patterns