Interface inheritance with IDisposable?

Question

I have the following inheritance hierarchy:

public interface IRepository<T> : IDisposable
{
    void Add(T model);
    void Update(T model);

    int GetCount();

    T GetById(int id);
    ICollection<T> GetAll();
}

public interface IAddressRepository : IRepository<Address>
{
}

And this code:

var adrs = new Address[]{
    new Address{Name="Office"}
};

using (IAddressRepository adrr = new AddressRepository())
    foreach (var a in adrs)
        adrr.Add(a);

However, this code does not compile. It gives me this error message:

Error   43  
'Interfaces.IAddressRepository': type used in a using statement must be
 implicitly convertible to 'System.IDisposable'

However, a parent of IAddressRepository inherits from IDisposable.

What is happening here? How do I make the code compile?

Answer 1

Works for me:

using System;

public class Address {}

public interface IRepository<T> : IDisposable
{
    void Add(T model);
    void Update(T model);
}

public interface IAddressRepository : IRepository<Address>
{
}

class Program
{
    public static void Main()
    {
        using (var repo = GetRepository())
        {
        }
    }

    private static IAddressRepository GetRepository()
    {
        // TODO: Implement :)
        return null;
    }
}

I suspect you may have two IAddressRepository interfaces. Are you sure it's Interfaces.IAddressRepository that extends IRepository<T>, and that that extends IDisposable?

Answer 2

My guess is that you are making a mistake- either you have not recompiled the assembly containing the IRepository<T> interface since you made it inherit from IDisposable, or you are referencing the wrong copy of it, or you are referencing some other IAddressRepository.

Try doing a Clean, then a Rebuild All, and check the paths on your references. If the projects are in the same solution, make sure you are referencing the project containing IRepository<T> / IAddressRepository and not the DLL.

Also make sure that AddressRepository actually implements IAddressRepository. It might just be reporting the wrong error.

EDIT: So the resolution seems to be that the assembly containing AddressRepository's parent class was not compiling. This caused the debugger to complain about AddressRepository not implementing IDisposable, rather than the (more sensible) " inaccessible due to its protection level" error compiling the class itself. My guess is you had that error too, but were addressing this one first.