Question

This is similar to another topic I recently posted, but perhaps this might be simpler and clearer:

I want to accomplish the following (or something very similar)…

IManageableEntryDao<IManageableEntry> dao = new CompanyNameDao(); 

… with the following classes:

public interface IManageableEntry {
    string Name { get; set; }
}

public class CompanyName : IManageableEntry {
    public string Name { get; set; }
}

public interface IManageableEntryDao<T> where T : IManageableEntry {
}

public class CompanyNameDao : IManageableEntryDao<CompanyName> {
}

If I try to do a cast as IManageableEntryDao<IManageableEntry>, I get a null.

Answer 1

See Variance in Generic Interfaces. Change the interface to IManageableEntryDao<out T> and it should work (unless the interface uses it in a way which makes this invalid).