C# inheritance and interfaces confusion

Question

I am trying to use fakes for EF 4.1 DataContext to test the repository without testing the database ( due to a deployment issue)

I am doing something like this

public interface IEmployeeContext
{
    IDbSet<Department> Departments { get; }
    IDbSet<Employee> Employees { get; }
    int SaveChanges();
}

public class EmployeeContext : DbContext, IEmployeeContext
{
    public IDbSet<Department> Departments { get; set; }
    public IDbSet<Employee> Employees { get; set; }
}

public class FakeEmployeeContext : IEmployeeContext
{
    public IDbSet<Department> Departments { get; set; }
    public IDbSet<Employee> Employees { get; set; }
    public FakeEmployeeContext ()
    {
        Departments = new FakeDbSet<Department>();
        Employees = new FakeDbSet<Employee>();
    }
}

which works great most of the time but my problem is that sometimes in my code i use things like :

context.Entry(department).State  = EntityState.Modified;

and it complains that

'IEmployeeContext' does not contain a definition for 'Entry'

I cannot seem to comprehend what i need to change in the pattern to allow me access to the context.Entry and context.Database sections

Is this a casting related problem? IEmployeeContext does not define a Entry attribute/function but instead its defined in the DbContext class. ((IEmployeeContext)context).Entry(department).State .. might solve your problem. — ba__friend
– ba__friend, Commented Jun 24, 2011 at 19:55
Seems like you want your FakeEmployeeContext to also inherit from DbContext, since EmployeeContext does — Rob
– Rob, Commented Jun 24, 2011 at 19:56
Casting as IEmployeeContext wouldnt help its already resolving to that .. and Casting to EmployeeContext would defeat the purpose of a n interface — MarkKGreenway
– MarkKGreenway, Commented Jun 24, 2011 at 21:12

Daniel Mann · Accepted Answer · 2011-06-24 19:58:33Z

1

The reason you're getting that specific error is because IEmployeeContext doesn't contain a method called Entry.

Entry is a member of DbContext.

edited Jun 24, 2011 at 19:58

answered Jun 24, 2011 at 19:53

Daniel Mann

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3 Comments

MarkKGreenway Over a year ago

If i make an Entry method part of the IEmployeeContext then I need to impliment it in in both EmployeeContext and FakeEmployeeContext and it is already implimented in EmployeeContext

Daniel Mann Over a year ago

Right, that method is coming from DbContext. A possible solution is to make your fake class inherit DbContext, although I haven't done enough with EF to be able to tell you if that will be of any use to you or not.

Daniel Mann Over a year ago

Just did some digging on this, and worst case, you can hide the Entry method from DbContext for the purposes of your fake employee context. It should, I believe, look like: public new DbEntityEntry<TEntity> Entry<TEntity>(TEntity entity) where TEntity: class {}

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