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
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