Trouble with abstract generic methods
- by DanM
Let's say I have a class library that defines a couple entity interfaces:
public interface ISomeEntity { /* ... */ }
public interface ISomeOtherEntity { /* ... */ }
This library also defines an IRepository interface:
public interface IRepository<TEntity> { /* ... */ }
And finally, the library has an abstract class called RepositorySourceBase (see below), which the main project needs to implement. The goal of this class is to allow the base class to grab new Repository objects at runtime. Because certain repositories are needed (in this example a repository for ISomeEntity and ISomeOtherEntity), I'm trying to write generic overloads of the GetNew<TEntity>() method.
The following implementation doesn't compile (the second GetNew() method gets flagged as "already defined" even though the where clause is different), but it gets at what I'm trying to accomplish:
public abstract class RepositorySourceBase // This doesn't work!
{
public abstract Repository<TEntity> GetNew<TEntity>()
where TEntity : SomeEntity;
public abstract Repository<TEntity> GetNew<TEntity>()
where TEntity : SomeOtherEntity;
}
The intended usage of this class would be something like this:
public class RepositorySourceTester
{
public RepositorySourceTester(RepositorySourceBase repositorySource)
{
var someRepository = repositorySource.GetNew<ISomeEntity>();
var someOtherRepository = repositorySource.GetNew<ISomeOtherEntity>();
}
}
Meanwhile, over in my main project (which references the library project), I have implementations of ISomeEntity and ISomeOtherEntity:
public class SomeEntity : ISomeEntity { /* ... */ }
public class SomeOtherEntity : ISomeOtherEntity { /* ... */ }
The main project also has an implementation for IRepository<TEntity>:
public class Repository<TEntity> : IRepository<TEntity>
{
public Repository(string message) { }
}
And most importantly, it has an implementation of the abstract RepositorySourceBase:
public class RepositorySource : RepositorySourceBase
{
public override Repository<SomeEntity> GetNew()
{
return new Repository<SomeEntity>("stuff only I know");
}
public override Repository<SomeOtherEntity> GetNew()
{
return new Repository<SomeOtherEntity>("other stuff only I know");
}
}
Just as with RepositorySourceBase, the second GetNew() method gets flagged as "already defined".
So, C# basically think I'm repeating the same method because there's no way to distinguish the methods from parameters, but if you look at my usage example, it seems like I should be able to distinguish which GetNew() I want from the generic type parameter, e.g, <ISomeEntity> or <ISomeOtherEntity>.
What do I need to do to get this to work?
