It might be better to make MyName (or whatever specific stuff needs to be done) abstract in Report.
-----Original Message----- From: Discussion of advanced .NET topics. [mailto:[EMAIL PROTECTED] On Behalf Of Brandon Willoughby Sent: Friday, December 14, 2007 1:55 PM To: ADVANCED-DOTNET@DISCUSS.DEVELOP.COM Subject: Re: [ADVANCED-DOTNET] Method that returns List<BaseClass> I think that if you add a different kind of report in the GetReports() method it might through an error though.... public List<Report> GetReports() { List<Report> reports = new List<Report>(); reports.Add(new Report()); reports.Add(new ReportA()); reports.Add(new ReportB()); return reports; } If the foreach loop is as you said: foreach (ReportA item in reports) WL(item.MyName); Then I think that the first two iterations would be fine, but the third might break (on second thought, the first iteration might break too). To be sure you could: foreach(Report r in reports) { if(r is ReportA) { // Do A-specific stuff } else if(r is ReportB) { // Do B-specific stuff } } I would test this but I am unable to at the moment. Brandon Ron Young wrote: > Indeed it does. Thank you. > > I was under the impression that if the method that returned derived reports ultimately returned a list of the base report, then the client would get the properties defined in the base report. > > But it's up to the client to determine what types of reports are in the list, so this works: > > // client-side > List<Report> reports = provider.GetReports(); > foreach (ReportA item in reports) > WL(item.MyName); > > Thanks again. > > ________________________________________ > From: Discussion of advanced .NET topics. [EMAIL PROTECTED] On Behalf Of Brandon Willoughby [EMAIL PROTECTED] > Sent: Friday, December 14, 2007 12:44 PM > To: ADVANCED-DOTNET@DISCUSS.DEVELOP.COM > Subject: Re: [ADVANCED-DOTNET] Method that returns List<BaseClass> > > I believe if you change your List<ReportA> (inside of GetReports()) to > type List<Report> it might work... > > Brandon > > Ron Young wrote: >> Is the following possible? The compiler tells me no: >> >> class Report >> { >> } >> >> class ReportA : Report >> { >> public string MyName = "ReportA"; >> } >> >> class ReportProvider >> { >> public List<Report> GetReports() >> { >> List<ReportA> reports = new List<ReportA>(); >> reports.Add(new Report()); >> return reports; >> } >> } >> >> I'd like to have that single method in ReportProvider, and hopefully a jumptable to return different types of reports: >> >> class ReportProvider >> { >> Dictionary<Type, Func<Criteria, List<Report>>> _mappings = new ... >> >> public ReportProvider() >> { >> _mappings.Add(typeof(BillableHoursReport, GetBillableHoursReport)); >> _mappings.Add(typeof(DetailByDateReport, GetDetailByDateReport)); >> } >> >> public IList<T> GetReport<T>(Criteria criteria) where T: Report >> { >> Type t = typeof(T); >> return _mappings[t].Invoke(criteria); >> } >> private IList<DetailByDateReport> GetDetailByDateReport(Criteria criteria) >> { >> List<DetailByDateReport> results = new ... >> // do stuff >> return results; >> } >> >> // other get report methods that return derived Report types >> } >> >> Thanks >> >> =================================== >> This list is hosted by DevelopMentor® http://www.develop.com >> >> View archives and manage your subscription(s) at http://discuss.develop.com > > =================================== > This list is hosted by DevelopMentor® http://www.develop.com > > View archives and manage your subscription(s) at http://discuss.develop.com > > =================================== > This list is hosted by DevelopMentor® http://www.develop.com > > View archives and manage your subscription(s) at http://discuss.develop.com =================================== This list is hosted by DevelopMentor® http://www.develop.com View archives and manage your subscription(s) at http://discuss.develop.com =================================== This list is hosted by DevelopMentor® http://www.develop.com View archives and manage your subscription(s) at http://discuss.develop.com
