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I know this doesnt compile but why shouldnt it?
public interface IReportService {
IList<IReport> GetAvailableReports();
IReport GetReport(int id);
}
public class ReportService : IReportService {
IList<IReport> GetAvailableReports() {
return new List<ConcreteReport>(); // This doesnt work
}
IReport GetReport(int id){
return new ConcreteReport(); // But this works
}
}
It’s because of covariance. You can get it to work in .NET 4 (read the link).