We're using EF Code first, and have a data context for our sales database. Additionally, we have a class that sits on top of our data context and does some basic CRUD operations.
For example, we have the following function:
public static T Create<T>(int userId, T entity) where T : class, IAllowCreate
{
if (entity == null)
throw new ArgumentNullException("entity");
using (SalesContext dc = new SalesContext())
{
dc.Set<T>().Add(entity);
dc.SaveChanges();
return entity;
}
}
I found an example of how to create fake contexts and IDBset properties. I started implementing that, but I ran in to an issue.
We use dc.Set() quite liberally (as seen above) in our code, as we attempt to create generic CRUD methods. Instead of having a ReadCustomer, ReadContact etc, we would just do Read(). However, dc.Set returns a DbSet, not an IDbSet, so I'm not able to mock that.
Has anyone been able to mock or fake DbContext and still use the Set functionality?
interface ISalesContext
{
IDbSet<T> GetIDbSet<T>();
}
class SalesContext : DbContext, ISalesContext
{
public IDbSet<T> GetIDbSet<T>()
{
return Set<T>();
}
}
I used a different name, but you can use the new operator if you prefer to hide the regular implementation.
Related
I am creating an application with ASP.NET MVC and Entity framework code first. I am using repository and unit of work pattern with influence of from following link.
http://www.asp.net/mvc/tutorials/getting-started-with-ef-5-using-mvc-4/implementing-the-repository-and-unit-of-work-patterns-in-an-asp-net-mvc-application
Here I have question about the implementation of Unit Of Work in that link unit of work is implemented via directly writing entities in class itself like.
public class UnitOfWork : IDisposable
{
private SchoolContext context = new SchoolContext();
private GenericRepository<Department> departmentRepository;
public GenericRepository<Department> DepartmentRepository
{
get
{
if (this.departmentRepository == null)
{
this.departmentRepository = new GenericRepository<Department>(context);
}
return departmentRepository;
}
}
}
Do you think that implementation is good enough because every time I add/remove entities I need to change my Unit of work class. I believe that Unit of work should not be dependent on entities. Because in my application based on Client feedback we are going to frequently add/remove entities.
I may sound stupid but let me know your views on that.
The Unit of Work pattern is already implemented in Entity Framework.
The DbContext is your Unit of Work.
Each IDbSet is a Repository.
using (var context = new SchoolContext()) // instantiate our Unit of Work
{
var department = context.Departments.Find(id);
}
There are a few flavors of the UnitOfWorkPattern. The one you are describing is a show everything, there is a hide everything approach as well. In the hide approach the unit of work references the DbContext.SaveChanges() method and nothing else; sounds like what you want.
public YourContext : DbContext, IContext{}
public interface IUnitOfWork{
void Commit();
}
public UnitOfWork : IUnitOfWork{
private readonly IContext _context;
//IOC should always inject the same instance of this, register it accordingly
public UnitOfWork(IContext context){
_context = context;
}
void Commit(){
// try catch the validation exception if you want to return the validations this
// way if your confident you've already validated you can put a void here or
// return the intfrom save changes make sure you handle the disposing properly,
// not going into that here you also may be doing other stuff here, have multiple
// "contexts" to save in a single transaction or we have contextProcessors that
// do stuff based on items in the context
_context.SaveChanges();
}
}
This leaves the issue of how you get your repositories into the classes that need them if you are not taking them from the UnitOfWork. This is best handled by an IOC framework. Again here there are a couple options. Once is to register the UnitOfWork as a single instance per request and have it injected into your custom Repository class.
public interface IRepository<T>
{
IQueryable<T> Records();
//other methods go here
}
public Repository : IRepository<T>
{
private IContext _context;
// same instance of context injected into the unit of work, this why when you Commit
// everything will save, this can get tricky if you start adding Add, Update and stuff
// but EF does have the support needed.
public Repository(IContext context)
{
_context = context;
}
public Records()
{
return _context.Set<T>();
}
}
public class SomeService : ISomeService{
private readonly _myObjectRepository;
public SomeService(IRepository<MyObject> myObjectRepository){
_myObjectRepository = myObjectRepository;
}
}
Personally I consider the IDbSet an sufficient abstraction so I no longer create repositories. In
order to inject the IDbSets from the context though you need to register them as instances that you
extract from the context in your IOC setup. This can be complex and depending on your skills you
could find yourself in the situation where you have to register each IDbSet which I know you are trying to avoid.
What's nice about using the IDbSet is you have access to simple methods like Add and can avoid some of the more complex parts of working with Entity and DbEntity in a generic sense.
public class SomeService : ISomeService {
private readonly _myObjectSet;
// requires specialized IOC configurations because you have to pull this instance from
// the instance of the context, personally don't know how to do this with a single
// registration so this has the same problem as having to add each new repository to the
// unit of work. In this case each new Entity I add to the context requires I add an IOC
// registration for the type.
public SomeService(IDbSet<MyObject> myObjectSet){
_myObjectSet= myObjectSet;
}
}
Try passing the SchoolContext to the GenericRepository:
public GenericRepository<T>
{
private SchoolContext _context;
public GenericRepository(SchoolContext context)
{
_context = context;
}
public Get(int id)
{
return _context.Set<T>().Find(id);
}
}
And use:
using(var context = new SchoolContext())
{
var departmentRepository = new GenericRepository<Department>(context);
var department = departmentRepository.Get(1);
}
I’m trying save some entities using breeze.js. Breeze is working fine and it saves all the changes as required. However, I have trouble validating and ensuring authorization is the server side. From what I’ve gather so far I guess the only way to do this is via examining the JObject passed into save bundles and constructing corresponding objects on the server side. I have to do this (instead of relying Breeze.SaveChanges as I have some logic on the server side). How do I do this? And how do I construct the Breeze.WebApi. SaveResult?
Idea of any other way of solving this problem is also very welcome
This should be done by implementing a custom EFContextProvider.
The code below implements a custom EFContextProvider for the Northwind database and was taken directly from the documentation on the breeze.com website .
public class NorthwindContextProvider: EFContextProvider<NorthwindIBContext> {
public NorthwindContextProvider() : base() { }
protected override bool BeforeSaveEntity(EntityInfo entityInfo) {
// return false if we don’t want the entity saved.
// prohibit any additions of entities of type 'Role'
if (entityInfo.Entity.GetType() == typeof(Role)
&& entityInfo.EntityState == EntityState.Added) {
return false;
} else {
return true;
}
}
protected override Dictionary<Type, List<EntityInfo>> BeforeSaveEntities(Dictionary<Type, List<EntityInfo>> saveMap) {
// return a map of those entities we want saved.
return saveMap;
}
}
#jaq316 is correct: a custom EFContextProvider is the place to intercept changes coming from the client. It is the place to both authorize and validate them . The documentation has more details. The essence of it is that you scrutinize the proposed changes within your overrides of the BeforeSaveEntity and BeforeSaveEntities virtual methods; alternatively you can attach handlers to the BeforeSaveEntityDelegate and BeforeSaveEntitiesDelegate.
So here is my thought on this one, since I am not using a ContextProvider at all. I am utilizing a SQL back-end and Ninject to inject a repository dependency into each controller I have. I have more items than the demo for "Todos" and want separate controllers out there and repositories as well. If I created the ContextProvider as shown by the breeze docs I would have one ContextProvider file with all the entities in it. This would be huge. If I separated them into separate contexts I would duplicating code in all the overrides.
Here is my Save Changes method in ContactFormController.cs :
[HttpPost]
public SaveResult SaveChanges(JObject saveBundle)
{
var sr = new SaveResult() { KeyMappings = new List<KeyMapping>(), Entities = new List<object>()};
dynamic entity = saveBundle["entities"][0];
ContactForm form = entity.ToObject<ContactForm>();
EntityState state = entity.entityAspect.entityState;
switch (state)
{
case EntityState.Added:
KeyMapping mapping = new KeyMapping(){EntityTypeName = typeof(ContactForm).ToString(), TempValue = form.Id };
var validationErrors = _contactFormService.ProcessContactForm(ref form).Cast<object>().ToList();
//if we succeed then update the mappings
if (validationErrors.Count == 0)
{
//setup the new mappings
mapping.RealValue = form.Id;
sr.KeyMappings.Add(mapping);
//link the entity
sr.Entities.Add(form);
}
else
{
sr.Errors = validationErrors;
}
break;
}
return sr;
}
I dynamically change the endpoints before saves on the client side so that each controller in my webapi has a SaveChanges() method. I then call into the appropriate repository to process the backend functions as needed. This way I can run mock code or actual SQL changes depending on the repo injected.
If their are errors on the Processing of the form then we cast our custom List list to a List and assign it to the Errors property of the SaveResult. If there are no errors we send back the new key mappings to be updated on the client.
Ideally I want to reduce all the code in this controller and perhaps abstract it out to a utility method so there is less repeat in every controller. I like this method because then I can create normal repositories and not have them depend on a ContextProvider. Breeze independent at that point.
In my generic repository I need to write generic Save method which will edit existed or add new entity depending on id.
public void Save<T>(T entity) where T : TEntity, IKeyId
{
if (ObjectSet.Any(r => (r as IKeyId).KeyId == entity.KeyId))
{
Edit(entity);
}
else
{
Add(entity);
}
}
But Linq generate exception when I try do Any( r=> (r as IKeyId)....
The 'TypeAs' expression with an input of type 'MyProg.DAL.Appeal' and a check of type 'Claimstrak.DAL.Interfaces.IKeyId' is not supported. Only entity types and complex types are supported in LINQ to Entities queries.
How to write it correct?
Well, the truth is that you dont need to use the ObjectSet, you can just use DbContext to do this, in a much more easy way.
Bu, i would tell that this is not a good pattern to use, to call a Save() in a repository. I would recomend that you consider the .SaveSession() of the Context only after all was done, this way you can do a lot of things befose making a round trip to te database.
So, you should make a method like this, but not call the SaveChanges(), instead of a Save() method, to a UpdateOrInsert() and them, after all is done you call the .Save()
But i will give the examplefollowing your request (but i dont recommend, i recommend you separate IUnitOfWork from IRepository)
See how the code is very simple:
interface IKeyId
{
int Id { get; set; }
}
DbContext context = new YourContext();
public bool Save<TEntity>(TEntity entity) where TEntity : class, IKeyId
{
return (entity.Id == 0) ? Add<TEntity>(entity) : Edit<TEntity>(entity);
}
public bool Edit<TEntity>(TEntity entity) where TEntity : class, IKeyId
{
var set = context.Set<TEntity>();
set.Attach(entity);
return true;
}
public bool Add<TEntity>(TEntity entity) where TEntity : class, IKeyId
{
var set = context.Set<TEntity>();
set.Add(entity);
return true;
}
I use a similar approach im my repositories, i have changed the T4 (.tt file) that generates the POCO classes from my database to excplicitly implement some interfaces that i have, such as IAuditable, IValidatable and other, so the T4 automaticaly implement those interfaces in the classes.
I've ran into some problems in an application where the .net process is running out of memory. One change I made in the application has been adding a lot of Linq to Sql classes. I'm wondering if there is an issue on how I'm creating my DataContext.
I could create my datacontext by creating the datacontext when I need it. Obviously if I was changing data, I would create a variable and hold the datacontext, because I would need the same data context in multiple statements.
Technique 1
public class SchoolRepository
{
DataBaseDataContext GetCtx()
{
return new DataBaseDataContext();
}
public List<School> GetSchools()
{
return GetCtx().Schools.ToList();
}
}
Here is another way I could create the DataContext. In this case I have a class field which holds a reference to a DataContext.
Technique 2:
public class SchoolRepository
{
private DataBaseDataContext _ctx = null;
DataBaseDataContext ctx
{
get { return _ctx = (_ctx ?? new DataBaseDataContext()); }
}
public List<School> GetSchools()
{
return ctx.Schools.ToList();
}
}
I have been using the second way (with a class variable), and I'm wondering if that could be causing the context to stick around longer than the first way--- because it would stick around as long as an instance of my class stuck around.
Perhaps I'm grasping at straws here-- but I'm wondering if one way is "safer" than the other way.
I have an application using ASP.NET MVC, Unity, and Linq to SQL.
The unity container registers the type AcmeDataContext which inherits from System.Data.Linq.DataContext, with a LifetimeManager using HttpContext.
There is a controller factory which gets the controller instances using the unity container. I set-up all my dependencies on the constructors, like this:
// Initialize a new instance of the EmployeeController class
public EmployeeController(IEmployeeService service)
// Initializes a new instance of the EmployeeService class
public EmployeeService(IEmployeeRepository repository) : IEmployeeService
// Initialize a new instance of the EmployeeRepository class
public EmployeeRepository(AcmeDataContext dataContext) : IEmployeeRepository
Whenever a constructor is needed, the unity container resolves a connection, which is used to resolve a data context, then a repository, then a service, and finally the controller.
The issue is that IEmployeeRepository exposes the SubmitChanges method, since the service classes DO NOT have a DataContext reference.
I have been told that the unit of work should be managed from outside the repositories, so it would seem I ought to remove SubmitChanges from my repositories. Why is that?
If this is true, does this mean that I have to declare an IUnitOfWork interface and make every service class dependent upon it? How else can I allow my service classes to manage the unit of work?
You shouldn't try to supply the AcmeDataContext itself to the EmployeeRepository. I would even turn the whole thing around:
Define a factory that allows creating a new unit of work for the Acme domain:
Create an abstract AcmeUnitOfWork that abstracts away LINQ to SQL.
Create a concrete factory that can allows creating new LINQ to SQL unit of works.
Register that concrete factory in your DI configuration.
Implement an InMemoryAcmeUnitOfWork for unit testing.
Optionally implement convenient extension methods for common operations on your IQueryable<T> repositories.
UPDATE: I wrote a blog post on this subject: Faking your LINQ provider.
Below is a step-by-step with examples:
WARNING: This will be a loooong post.
Step 1: Defining the factory:
public interface IAcmeUnitOfWorkFactory
{
AcmeUnitOfWork CreateNew();
}
Creating a factory is important, because the DataContext implement IDisposable so you want to have ownership over the instance. While some frameworks allow you to dispose objects when not needed anymore, factories make this very explicit.
Step 2: Creating an abstract unit of work for the Acme domain:
public abstract class AcmeUnitOfWork : IDisposable
{
public IQueryable<Employee> Employees
{
[DebuggerStepThrough]
get { return this.GetRepository<Employee>(); }
}
public IQueryable<Order> Orders
{
[DebuggerStepThrough]
get { return this.GetRepository<Order>(); }
}
public abstract void Insert(object entity);
public abstract void Delete(object entity);
public abstract void SubmitChanges();
public void Dispose()
{
this.Dispose(true);
GC.SuppressFinalize(this);
}
protected abstract IQueryable<T> GetRepository<T>()
where T : class;
protected virtual void Dispose(bool disposing) { }
}
There are some interesting things to note about this abstract class. The Unit of Work controls and creates the Repositories. A repository is basically something that implements IQueryable<T>. The repository implements properties that return a specific repository. This prevents users from calling uow.GetRepository<Employee>() and this creates a model that is very close to what you are already doing with LINQ to SQL or Entity Framework.
The unit of work implements Insert and Delete operations. In LINQ to SQL these operations are placed on the Table<T> classes, but when you try to implement it this way it will prevent you from abstracting LINQ to SQL away.
Step 3. Create a concrete factory:
public class LinqToSqlAcmeUnitOfWorkFactory : IAcmeUnitOfWorkFactory
{
private static readonly MappingSource Mapping =
new AttributeMappingSource();
public string AcmeConnectionString { get; set; }
public AcmeUnitOfWork CreateNew()
{
var context = new DataContext(this.AcmeConnectionString, Mapping);
return new LinqToSqlAcmeUnitOfWork(context);
}
}
The factory created a LinqToSqlAcmeUnitOfWork based on the AcmeUnitOfWork base class:
internal sealed class LinqToSqlAcmeUnitOfWork : AcmeUnitOfWork
{
private readonly DataContext db;
public LinqToSqlAcmeUnitOfWork(DataContext db) { this.db = db; }
public override void Insert(object entity)
{
if (entity == null) throw new ArgumentNullException("entity");
this.db.GetTable(entity.GetType()).InsertOnSubmit(entity);
}
public override void Delete(object entity)
{
if (entity == null) throw new ArgumentNullException("entity");
this.db.GetTable(entity.GetType()).DeleteOnSubmit(entity);
}
public override void SubmitChanges();
{
this.db.SubmitChanges();
}
protected override IQueryable<TEntity> GetRepository<TEntity>()
where TEntity : class
{
return this.db.GetTable<TEntity>();
}
protected override void Dispose(bool disposing) { this.db.Dispose(); }
}
Step 4: Register that concrete factory in your DI configuration.
You know self best how to register the IAcmeUnitOfWorkFactory interface to return an instance of the LinqToSqlAcmeUnitOfWorkFactory, but it would look something like this:
container.RegisterSingle<IAcmeUnitOfWorkFactory>(
new LinqToSqlAcmeUnitOfWorkFactory()
{
AcmeConnectionString =
AppSettings.ConnectionStrings["ACME"].ConnectionString
});
Now you can change the dependencies on the EmployeeService to use the IAcmeUnitOfWorkFactory:
public class EmployeeService : IEmployeeService
{
public EmployeeService(IAcmeUnitOfWorkFactory contextFactory) { ... }
public Employee[] GetAll()
{
using (var context = this.contextFactory.CreateNew())
{
// This just works like a real L2S DataObject.
return context.Employees.ToArray();
}
}
}
Note that you could even remove the IEmployeeService interface and let the controller use the EmployeeService directly. You don't need this interface for unit testing, because you can replace the unit of work during testing preventing the EmployeeService from accessing the database. This will probably also save you a lot of DI configuration, because most DI frameworks know how to instantiate a concrete class.
Step 5: Implement an InMemoryAcmeUnitOfWork for unit testing.
All these abstractions are there for a reason. Unit testing. Now let's create a AcmeUnitOfWork for unit testing purposes:
public class InMemoryAcmeUnitOfWork: AcmeUnitOfWork, IAcmeUnitOfWorkFactory
{
private readonly List<object> committed = new List<object>();
private readonly List<object> uncommittedInserts = new List<object>();
private readonly List<object> uncommittedDeletes = new List<object>();
// This is a dirty trick. This UoW is also it's own factory.
// This makes writing unit tests easier.
AcmeUnitOfWork IAcmeUnitOfWorkFactory.CreateNew() { return this; }
// Get a list with all committed objects of the requested type.
public IEnumerable<TEntity> Committed<TEntity>() where TEntity : class
{
return this.committed.OfType<TEntity>();
}
protected override IQueryable<TEntity> GetRepository<TEntity>()
{
// Only return committed objects. Same behavior as L2S and EF.
return this.committed.OfType<TEntity>().AsQueryable();
}
// Directly add an object to the 'database'. Useful during test setup.
public void AddCommitted(object entity)
{
this.committed.Add(entity);
}
public override void Insert(object entity)
{
this.uncommittedInserts.Add(entity);
}
public override void Delete(object entity)
{
if (!this.committed.Contains(entity))
Assert.Fail("Entity does not exist.");
this.uncommittedDeletes.Add(entity);
}
public override void SubmitChanges()
{
this.committed.AddRange(this.uncommittedInserts);
this.uncommittedInserts.Clear();
this.committed.RemoveAll(
e => this.uncommittedDeletes.Contains(e));
this.uncommittedDeletes.Clear();
}
protected override void Dispose(bool disposing)
{
}
}
You can use this class in your unit tests. For instance:
[TestMethod]
public void ControllerTest1()
{
// Arrange
var context = new InMemoryAcmeUnitOfWork();
var controller = new CreateValidController(context);
context.AddCommitted(new Employee()
{
Id = 6,
Name = ".NET Junkie"
});
// Act
controller.DoSomething();
// Assert
Assert.IsTrue(ExpectSomething);
}
private static EmployeeController CreateValidController(
IAcmeUnitOfWorkFactory factory)
{
return new EmployeeController(return new EmployeeService(factory));
}
Step 6: Optionally implement convenient extension methods:
Repositories are expected to have convenient methods such as GetById or GetByLastName. Of course IQueryable<T> is a generic interface and does not contains such methods. We could clutter our code with calls like context.Employees.Single(e => e.Id == employeeId), but that's really ugly. The perfect solution to this problem is: extension methods:
// Place this class in the same namespace as your LINQ to SQL entities.
public static class AcmeRepositoryExtensions
{
public static Employee GetById(this IQueryable<Employee> repository,int id)
{
return Single(repository.Where(entity => entity.Id == id), id);
}
public static Order GetById(this IQueryable<Order> repository, int id)
{
return Single(repository.Where(entity => entity.Id == id), id);
}
// This method allows reporting more descriptive error messages.
[DebuggerStepThrough]
private static TEntity Single<TEntity, TKey>(IQueryable<TEntity> query,
TKey key) where TEntity : class
{
try
{
return query.Single();
}
catch (Exception ex)
{
throw new InvalidOperationException("There was an error " +
"getting a single element of type " + typeof(TEntity)
.FullName + " with key '" + key + "'. " + ex.Message, ex);
}
}
}
With these extension methods in place, it allows you to call those GetById and other methods from your code:
var employee = context.Employees.GetById(employeeId);
What the nicest thing is about this code (I use it in production) is that -once in place- it saves you from writing a lot of code for unit testing. You will find yourself adding methods to the AcmeRepositoryExtensions class and properties to the AcmeUnitOfWork class when new entities are added to the system, but you don't need to create new repository classes for production or testing.
This model has of course some shortcomes. The most important perhaps is that LINQ to SQL isn't abstract away completely, because you still use the LINQ to SQL generated entities. Those entity contain EntitySet<T> properties which are specific to LINQ to SQL. I haven't found them to be in the way of proper unit testing, so for me it's not a problem. If you want you can always use POCO objects with LINQ to SQL.
Another shortcome is that complicated LINQ queries can succeed in test but fail in production, because of limitations (or bugs) in the query provider (especially the EF 3.5 query provider sucks). When you do not use this model, you are probably writing custom repository classes that are completely replaced by unit test versions and you will still have the problem of not being able to test queries to your database in unit tests. For this you will need integration tests, wrapped by a transaction.
A last shortcome of this design is the use of Insert and Delete methods on the Unit of Work. While moving them to the repository would force you to have a design with an specific class IRepository<T> : IQueryable<T> interface, it prevents you from other errors. In the solution I use myself I also have InsertAll(IEnumerable) and DeleteAll(IEnumerable) methods. It is however easy to mistype this and write something like context.Delete(context.Messages) (note the use of Delete instead of DeleteAll). This would compile fine, because Delete accepts an object. A design with delete operations on the repository would prevent such statement from compiling, because the repositories are typed.
UPDATE: I wrote a blog post on this subject that describes this solution in even more detail: Faking your LINQ provider.
I hope this helps.
If combining unit of work and repository patterns, some people advocate that UoW should be managed outside of repository so that you could create two repositories (say, CustomerRepository and OrderRepository) and pass them the same UoW instance ensuring that all the changes to the DB will be done atomically when you finally call UoW.Complete().
In a mature DDD solution however, there should not be need for both UoW and a repository. This is because is such a solution aggregate boundaries are defined is such a way, that there is no need of atomic changes involving more than one repository.
Does this answer your question?