Develop Reference

Confusion over using of UnitOfWork in Repository Pattern

It's a week I have been dealing with Repository pattern, somehow I have implemented something, a generic repository:
private CentralEntities db = null;
private DbSet<T> table = null;
public RepositoryTest()
{
this.db = new CentralEntities();
table = db.Set<T>();
}
public RepositoryTest(CentralEntities db)
{
this.db = db;
table = db.Set<T>();
}
public IEnumerable<T> SelectAll()
{
return table.Take(10).ToList();
}
Here is my IRepository:
public interface IRepositoryTest<T> where T:class
{
IEnumerable<T> SelectAll();
}
Here in my Controller I implemented like the following and it works:
public class DashbrdController : Controller
{
IRepositoryTest<Event> _repository = null;
public DashbrdController(IRepositoryTest<Event> _repository)
{
this._repository = _repository;
}
public DashbrdController()
{
this._repository = new RepositoryTest<Event>();
}
public ActionResult DashBrd()
{
var rslt= _repository.SelectAll().Take(10);
return View(rslt);
}
}
First I do not how to implement Iunitofwork and UnitOfWork, and second apart from creating a single gate for update or insert, whats the usage of UnitOfWork? what kind of problem can it solve in the above example?

Please refer to the section below for detail understanding of UOW and Repository:
1) You create Generic Repository (The base of all the data source):
public class GenericRepository : IGenericRepository where T :
class
{
protected DbContext _entities;
protected readonly IDbSet<T> _dbset;
public GenericRepository(DbContext context)
{
_entities = context;
_dbset = context.Set<T>();
}
public IEnumerable<T> GetAll()
{
return _dbset.AsEnumerable();
}
public IEnumerable<T> FindBy(System.Linq.Expressions.Expression<Func<T, bool>> predicate)
{
IEnumerable<T> query = _dbset.Where(predicate).AsEnumerable();
return query;
}
public virtual T GetSingle(System.Linq.Expressions.Expression<Func<T, bool>> predicate)
{
T query = _dbset.Where(predicate).FirstOrDefault();
return query;
}
public virtual void Add(T entity)
{
_dbset.Add(entity);
}
public virtual void Delete(T entity)
{
_dbset.Remove(entity);
}
public virtual void Edit(T entity)
{
_entities.Entry(entity).State = EntityState.Modified;
}
public virtual void Attach(T entity)
{
_dbset.Attach(entity);
}
public virtual void Save()
{
_entities.SaveChanges();
}
}
2) Then you create a Unit Of Work (Generic that adds the instance of Repository)
public sealed class GenericUnitOfWork : IGenericUnitOfWork, IDisposable
{
private ApplicationDbContext entities = null;
private ApplicationUserManager _userManager;
public GenericUnitOfWork()
{
entities = new ApplicationDbContext();
}
public Dictionary<Type, object> repositories = new Dictionary<Type, object>();
public IGenericRepository<T> Repository<T>() where T : class
{
if (repositories.Keys.Contains(typeof(T)) == true)
{
return repositories[typeof(T)] as IGenericRepository<T>;
}
IGenericRepository<T> repo = new GenericRepository<T>(entities);
repositories.Add(typeof(T), repo);
return repo;
}
public int Commit()
{
return entities.SaveChanges();
}
private bool disposed = false;
private void Dispose(bool disposing)
{
if (!this.disposed)
{
if (disposing)
{
entities.Dispose();
}
}
this.disposed = true;
}
public void Dispose()
{
Dispose(true);
GC.SuppressFinalize(this);
}
}
3) Then you call UnitOfWork from your controller, that creates instance of Repository in Generic Form
public class DashbrdController : Controller
{
private GenericUnitOfWork uow = null;
public DashbrdController()
{
uow = new GenericUnitOfWork();
}
public ActionResult DashBrd()
{
var rslt = uow.Repository<Event>().GetAll().ToList();
return View(rslt);
}
}
The unit of work class coordinates the work of multiple repositories by creating a single database context class shared by all of them.
For a specific user action (say adding a event), all the transactions like insert/update/delete and so on are done in one single transaction, rather then doing multiple database transactions. This means, one unit of work here involves insert/update/delete operations, all in one single transaction.
Please make the interfaces with the implementation classes provided above. Let me know if problem occurs in that.
Hope if helps.

C# Repository with multiple constraints and inheritance

i wasn't able to find a similar issue but feel free to redirect me if i just missed it.
I am trying to get familiar with the Repository pattern.
I'll give you an example of the code i'm trying to get to work unsuccessfully.
These are the classes and interfaces that represent the entity i'm using.
public class AbsObj
{
public string Code { get; set; }
}
public interface IAbsObj
{
bool Save();
}
public class User : AbsObj
{
public string Language{get; set;}
}
public class DbUser : User, IAbsObj
{
public bool Save()
{
return true;
}
}
Then to the repository Interface
public interface IRepository<T>
{
void Add(T value);
void Update(T value);
void Delete(T value);
}
The generic Repository
public class Repository<T> : IRepository<T> where T : AbsObj, IAbsObj
{
protected List<T> _lst;
public Repository()
{
_lst = new List<T>();
}
public void Add(T value)
{
}
public void Update(T value)
{
}
public void Delete(T value)
{
}
public bool Save()
{
for (int i = 0; i < _lst.Count; i++)
{
_lst[i].Save();
}
return true;
}
}
Then a more specific repository, which should handle the loading of the users from the db:
public class UserRepository<T> : Repository<T> where T : AbsObj, IAbsObj
{
public void Load()
{
DbUser us = new DbUser();
us.Code = "Cod";
us.Language = "IT";
_lst.Add(us);
}
}
I created the DBUser class just to have the freedom to create an XMLUser in the future which would handle a different type of saving.
It inherits from User which in turn inherits from AbsObj.
It implements IAbsObj.
Nonetheless i got a compile time error when i try to add to the list the DbUser object created, stating that it's impossible to convert from DBUser to T.
Given the constraints i tought it was possible: what am i missing here?
Thanks in advance for any help!

Your UserRepository definition could be:
public class UserRepository : Repository<DbUser>
{
....
}
But since you want to make it generic for XMLUser as well:
public class UserRepository<T> : Repository<T> where T: User, new()
{
public void Load()
{
User us = new T() as User;
us.Code = "Cod";
us.Language = "IT";
_lst.Add(us);
}
}
To use:
new UserRepostitory<DbUser>();
new UserRepostitory<XmlUser>();

Setting the connection string of a DBContext in my repository class using Ninject

I have an MVC 5 application that uses EF 6 and implements Repository pattern with dependency injection using the DI container Ninject. The connection string for the dbcontext is stored in the Web.config file which the EF Context properly finds. Everything works fine. Lately, I have a requirement that the connection to my DBContext need to be determined at runtime and connect to different databases (but with exactly the same structure). So, I need to change the sql connectionstring part from the entity connectionstring at run-time before the repository is instantiated. I would really appreciate some help in doing it. I am not a DI guru; know just enough Ninject to get my things going.
Here is my Repository Base Interface:
public interface IRepositoryBase<T> where T : class
{
void Add(T entity, string userGuid = "");
void Delete(T entity);
// ... removed other method signatures for brevity
}
My Repository base implementation:
public abstract class RepositoryBase<D, T> : IRepositoryBase<T>, IDisposable
where T : class
where D : DbContext, new()
{
private Guid? currUserGuid = null;
private D dataContext;
protected D DataContext
{
get
{
if (dataContext == null)
dataContext = new D();
return dataContext;
}
set { dataContext = value; }
}
public IQueryable<T> FindBy(Expression<Func<T, bool>> predicate)
{
return DataContext.Set<T>().Where(predicate);
}
public virtual IQueryable<T> GetAll()
{
IQueryable<T> query = DataContext.Set<T>();
return query;
}
public virtual void Delete(T entity)
{
OperationStatus stat = TryDelete(entity);
}
// .... removed rest for brevity
}
Interface and implementation for concrete class:
public interface ICustomerRepository : IRepositoryBase<Customer>
{
Customer GetCustomerAndStatus( Guid custGuid );
}
public class CustomerRepository : RepositoryBase<PCDataEFContext, Customer>, ICustomerRepository
{
public Customer GetCustomerAndStatus( Guid custGuid )
{
return DataContext.Customers.Include( x => x.CustStatusType )
.SingleOrDefault( x => x.PKGuid == custGuid );
}
}
My Ninject dependency resolver:
public class NinjectDependencyResolver : IDependencyResolver
{
private IKernel kernel;
public NinjectDependencyResolver()
{
kernel = new StandardKernel();
AddBindings();
}
public IKernel Kernel { get { return kernel; } }
private void AddBindings()
{
kernel.Bind<ICustomerRepository>().To<CustomerRepository>();
// ... other bindings are omitted for brevity
}
}
and finally, here is my Entity Framework generated DBContext:
public partial class PCDataEFContext : DbContext
{
public PCDataEFContext()
: base("name=PCDataEFContext")
{
}
protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
throw new UnintentionalCodeFirstException();
}
public virtual DbSet<Customer> Customers { get; set; }
}
All the above code works great! But as I said in the beginning, I don't know how to inject the connection string into my Repositorybase class at runtime so that I don't have to modify any of my inherited repositories (I have plenty of them). Someone please help.
Babu.

Could you do it like this?
public partial class PCDataEFContext : DbContext
{
public PCDataEFContext()
: base(Util.GetTheConnectionString())
{ }
}
public class MyDerivedContext : PCDataEFContext
{
public MyDerivedContext()
: base()
{ }
}
class Util
{
public static string GetTheConnectionString()
{
// return the correct name based on some logic...
return "name=PCDataEFContext";
}
}
Another way of doing it, could be in the RepositorBase class you defined, by altering the connectionstring after the creation of the dbcontext:
protected D DataContext
{
get
{
if (dataContext == null)
{
dataContext = new D();
dataContext.Database.Connection.ConnectionString = "the new connectionstring";
}
return dataContext;
}
set { dataContext = value; }
}

Crud operations with unit of work and generic repository

I am working on crud operations in mvc 4.0 with unitofwork and generic repository with Ninject for DI.
I am able to get a particular record from a table, I am even able to get all the records from the table.
but I am not able to insert a new record in the database table. I am not getting any error/exception and it is running each statement
cleanly but there is no effect in database below is my controller where I am using the repository and unitof work.
Can somebody tell me where I am wron or what code/statements I have left in this code. I ahve checked it lot of time and I am stucked now.
Not getting the problem
Controller:
private IUnitOfWork _unitOfWork;
private IRepository<tbl_Employee> _Repo;
private IRepository<tbl_Department> _Department;
public HomeController( IUnitOfWork UOW, IRepository<tbl_Employee> Repository, IRepository<tbl_Department> Depart)
{
this._unitOfWork = UOW;
this._Repo = Repository;
this._Department = Depart;
}
//This runs successfully and gets all the records in the view page and I am displaying all records using foreach in div structure
public ActionResult Index()
{
EmployeeModel ObjModel = new EmployeeModel();
ObjModel.Employees = this._Repo.GetALL();
//ObjModel.Employees = this._Employee.GetEmployees();
return View(ObjModel);
}
//This also runs successfully and it brought me a single record on selection of particular record from employee listing.
public ActionResult EmployeeDetail(string id)
{
EmployeeDetailModel ObjModel = new EmployeeDetailModel();
if (!string.IsNullOrEmpty(id))
{
var Employee = this._Repo.Find(Convert.ToInt32(id));
if (Employee != null)
{
ObjModel.InjectFrom(Employee);
}
}
return View(ObjModel);
}
// Here is the problem . Not able to insert the record. The model object is not empty . I have checked it and there is no error.It brought me a message
"Employee Created Successfully but in database there is no record.
public ActionResult SaveEmployee(EmployeeDetailModel Model)
{
string Msg = string.Empty;
try
{
tbl_Employee ObjEmployee = new tbl_Employee();
ObjEmployee.InjectFrom(Model);
if (Model.Male)
{
ObjEmployee.Sex = "m";
}
else
{
ObjEmployee.Sex = "f";
}
ObjEmployee.Department_Id = Model.Dept_id;
ObjEmployee.Salary = Convert.ToInt32(Model.Salary);
this._Repo.Insert(ObjEmployee);
this._unitOfWork.Commit();
Msg = "Employee Created Successfully";
}
catch
{
Msg = "Error occurred while creating the employee, Please try again.";
}
return Json(new { Message = Msg });
}
/// Repository interface
public interface IRepository<T> where T : class
{
void Insert(T entity);
void Delete(T entity);
void Update(T entity);
T Find(int key);
IEnumerable<T> GetALL();
}
Repository class
public class Repository<T> : Connection, IRepository<T> where T : class
{
private readonly DbSet<T> _dbSet;
public Repository()
{
_dbSet = _dbContext.Set<T>();
}
public void Insert(T entity)
{
_dbSet.Add(entity);
}
public void Delete(T entity)
{
_dbSet.Remove(entity);
}
public void Update(T entity)
{
var updated = _dbSet.Attach(entity);
_dbContext.Entry(entity).State = EntityState.Modified;
//_dataContext.Entry(item).State = EntityState.Modified;
}
public T Find(int Key)
{
var dbResult = _dbSet.Find(Key);
return dbResult;
}
public IEnumerable<T> GetALL()
{
return _dbSet;
}
}
UnitofWork Interface
public interface IUnitOfWork : IDisposable
{
void Commit();
}
Unit of work class
public class UnitOfWork : Connection, IUnitOfWork
{
private bool _disposed;
public void Commit()
{
_dbContext.SaveChanges();
}
public void Dispose()
{
Dispose(true);
// Take yourself off the Finalization queue to prevent finalization code for object from executing a second time.
GC.SuppressFinalize(this);
}
protected virtual void Dispose(bool disposing)
{
// Check to see if Dispose has already been called.
if (!_disposed)
{
// If disposing equals true, dispose all managed and unmanaged resources.
if (disposing)
{
// Dispose managed resources.
if (_dbContext != null)
{
_dbContext.Dispose();
}
}
}
_disposed = true;
}
}
My UnitofWork and Repository class derives from connection class where dbcontext is defined.
public abstract class Connection
{
protected db_TestEntities _dbContext;
public Connection()
{
this._dbContext = new db_TestEntities();
}
}
Is it that my dbContext is creating a new instance everytime like explained Here
and if yes then how can I resolve it.

tbl_Employee ObjEmployee = new tbl_Employee();
ObjEmployee.InjectFrom(Model);
if (Model.Male)
{
ObjEmployee.Sex = "m";
}
else
{
ObjEmployee.Sex = "f";
}
ObjEmployee.Department_Id = Model.Dept_id;
ObjEmployee.Salary = Convert.ToInt32(Model.Salary);
this._Repo.Insert(ObjEmployee);
After this, you should see your object mapped by EF in local memory.
this._unitOfWork.Commit();
Here your object should be pushed to database. dbContext.SaveChanges() return number of changed records which should be in your case 1.
Msg = "Employee Created Successfully";
Update:
So the problem is in your Connection class as you suggested.
I would create your DbContext in one place and then pass it to repository and unit of work. You could also create DbContext in unit of work constructor and then pass UOW to repository. This is one of my older implementation of this:
public class EntityFrameworkUnitOfWork : IUnitOfWork
{
private ForexDbContext dbContext;
internal ForexDbContext DbContext
{
get { return dbContext ?? (dbContext = new ForexDbContext()); }
}
internal DbSet<T> Set<T>()
where T : class
{
return DbContext.Set<T>();
}
public void Dispose()
{
if(dbContext == null) return;
dbContext.Dispose();
dbContext = null;
}
public void SaveChanges()
{
int result = DbContext.SaveChanges();
}
public ITransaction BeginTransaction()
{
return new EntityFrameworkTransaction(DbContext.BeginTransaction());
}
}

public class ContactsRepositoryWithUow : IRepository<Contact>
{
private SampleDbEntities entities = null;
public ContactsRepositoryWithUow(SampleDbEntities _entities)
{
entities = _entities;
}
public IEnumerable<Contact> GetAll(Func<Contact, bool> predicate = null)
{
if (predicate != null)
{
if (predicate != null)
{
return entities.Contacts.Where(predicate);
}
}
return entities.Contacts;
}
public Contact Get(Func<Contact, bool> predicate)
{
return entities.Contacts.FirstOrDefault(predicate);
}
public void Add(Contact entity)
{
entities.Contacts.AddObject(entity);
}
public void Attach(Contact entity)
{
entities.Contacts.Attach(entity);
entities.ObjectStateManager.ChangeObjectState(entity, EntityState.Modified);
}
public void Delete(Contact entity)
{
entities.Contacts.DeleteObject(entity);
}
}
Please find answer in below link for more details
Crud Operation with UnitOfWork

UnitOfWork with Unity and Entity Framework

Hi I am using Unity to manage my service layers, which in turn speak to UnitOfWork which manages all the repositories.
Some of my services call other services, my question is how can i pass the same UnitOfWork between service layers?
In my case all controller actions are initiated from a GUI on each button action or event on a timer, this is why I have a factory to create UnitOfWork on demand, but it is causing issues as i dont know how to pass this UnitOfWork between services.
Especially difficult is knowing how to get this specific UnitOfWork instance injected into the service constructor. Please note that some of the services may be long running (10 minutes or so on a background thread), i don't know if that has any impact on the design or not.
Currently the service that is called from the other service is then creating its own UnitOfWork which is causing issues for both transactional design, and Entity framework entity tracking.
Suggestions very welcome!
class OtherService : IOtherService
{
public OtherService(IUnitOfWorkFactory unitOfworkFactory,
ISettingsService settingsService)
{
UnitOfWorkFactory = unitOfworkFactory;
SettingsService = settingsService;
}
IUnitOfWorkFactory UnitOfWorkFactory;
ISettingsService SettingsService;
function SomeSeviceCall()
{
// Perhaps one way is to use a factory to instantiate a
// SettingService, and pass in the UnitOfWork here?
// Ideally it would be nice for Unity to handle all of
// the details regardless of a service being called from
// another service or called directly from a controller
// ISettingsService settingsService =
// UnityContainer.Resolve<ISettingService>();
using (var uow = UnitOfWorkFactory.CreateUnitOfWork())
{
var companies = uow.CompaniesRepository.GetAll();
foreach(Company company in companies)
{
settingsService.SaveSettings(company, "value");
company.Processed = DateTime.UtcNow();
}
uow.Save();
}
}
}
class SettingsService : ISettingsService
{
public SettingsService(IUnitOfWorkFactory unitOfworkFactory)
{
UnitOfWorkFactory = unitOfworkFactory;
}
IUnitOfWorkFactory UnitOfWorkFactory;
// ISettingsService.SaveSettings code in another module...
function void ISettingsService.SaveSettings(Company company,
string value)
{
// this is causing an issue as it essentially creates a
// sub-transaction with the new UnitOfWork creating a new
// Entiy Framework context
using (var uow = UnitOfWorkFactory.CreateUnitOfWork())
{
Setting setting = new Setting();
setting.CompanyID = company.CompanyID;
setting.SettingValue = value;
uow.Insert(setting);
uow.Save();
}
}
}

Hi I've been battling with this problem this is what I've come up with...
public class UnitOfWorkFactory
{
private static readonly Hashtable _threads = new Hashtable();
private const string HTTPCONTEXTKEY =
"AboutDbContext.UnitOfWorkFactory";
public static IUnitOfWork Create()
{
IUnitOfWork unitOfWork = GetUnitOfWork();
if (unitOfWork == null || unitOfWork.IsDisposed)
{
unitOfWork = new UnitOfWork();
SaveUnitOfWork(unitOfWork);
}
return unitOfWork;
}
public static IUnitOfWork GetUnitOfWork()
{
if (HttpContext.Current != null)
{
if (HttpContext.Current.Items.Contains(HTTPCONTEXTKEY))
{
return (IUnitOfWork)HttpContext
.Current.Items[HTTPCONTEXTKEY];
}
return null;
}
var thread = Thread.CurrentThread;
if (string.IsNullOrEmpty(thread.Name))
{
thread.Name = Guid.NewGuid().ToString();
return null;
}
lock (_threads.SyncRoot)
{
return (IUnitOfWork)_threads[Thread.CurrentThread.Name];
}
}
private static void SaveUnitOfWork(IUnitOfWork unitOfWork)
{
if (HttpContext.Current != null)
{
HttpContext.Current.Items[HTTPCONTEXTKEY] = unitOfWork;
}
else
{
lock (_threads.SyncRoot)
{
_threads[Thread.CurrentThread.Name] = unitOfWork;
}
}
}
public static void DisposeUnitOfWork(IUnitOfWork unitOfWork)
{
if (HttpContext.Current != null)
{
HttpContext.Current.Items.Remove(HTTPCONTEXTKEY);
}
else
{
lock (_threads.SyncRoot)
{
_threads.Remove(Thread.CurrentThread.Name);
}
}
}
}
public interface IUnitOfWork : IDisposable
{
void Commit();
bool IsDisposed { get; }
}
public class UnitOfWork : MyContext
{
}
public abstract class Repository<T>
: IRepository<T>, IDisposable where T : class
{
private UnitOfWork _context;
private UnitOfWork Context
{
get
{
if (_context == null || _context.IsDisposed)
return _context = GetCurrentUnitOfWork<UnitOfWork>();
return _context;
}
}
public TUnitOfWork GetCurrentUnitOfWork<TUnitOfWork>()
where TUnitOfWork : IUnitOfWork
{
return (TUnitOfWork)UnitOfWorkFactory.GetUnitOfWork();
}
public IEnumerable<T> Get(Expression<Func<T, bool>> predicate)
{
return Context.Set<T>().Where(predicate).ToList();
}
public bool Exists(Expression<Func<T, bool>> predicate)
{
return Context.Set<T>().Any(predicate);
}
public T First(Expression<Func<T, bool>> predicate)
{
return Context.Set<T>().Where(predicate).FirstOrDefault();
}
public IEnumerable<T> GetAll()
{
return Context.Set<T>().ToList();
}
public IEnumerable<T> GetAllOrderBy(Func<T, object> keySelector)
{
return Context.Set<T>().OrderBy(keySelector).ToList();
}
public IEnumerable<T> GetAllOrderByDescending(Func<T, object> keySelector)
{
return Context.Set<T>().OrderByDescending(keySelector).ToList();
}
public void Commit()
{
Context.SaveChanges();
}
public void Add(T entity)
{
Context.Set<T>().Add(entity);
}
public void Update(T entity)
{
Context.Entry(entity).State = EntityState.Modified;
}
public void Delete(T entity)
{
Context.Set<T>().Remove(entity);
}
public void Dispose()
{
if (Context != null)
{
Context.Dispose();
}
GC.SuppressFinalize(this);
}
}
public class MyContext : DbContext, IUnitOfWork
{
public DbSet<Car> Cars { get; set; }
public void Commit()
{
SaveChanges();
}
protected override void Dispose(bool disposing)
{
IsDisposed = true;
UnitOfWorkFactory.DisposeUnitOfWork(this);
base.Dispose(disposing);
}
public bool IsDisposed { get; private set; }
}
Then I can do:
using (var unitOfWork = UnitOfWorkFactory.Create())
{
_carRepository.Add(new Car
{
Make = "Porshe", Name = "Boxter"
});
_carRepository.Commit();
}

You could use some kind of "current" unit of work which is tied to current thread and explicitly resolved in service code. You need class to hold thread static instance of UoW to achieve this. However, this is not very good solution.

You be the judge...
I think you are double doing it.
Point 1:
http://www.britannica.com/topic/Occams-razor
Point 2:
From the F2 object browser description of EF main object, the DBContext...
public class DbContext
Member of System.Data.Entity
Summary:
A DbContext instance represents a combination of the Unit Of Work and Repository patterns such that it can be used to query from a database and group together changes that will then be written back to the store as a unit.