Casting an Anonymous type to a known type.

Question

I have a method that contains the following Linq to SQL code:

    public List<L2SBusinessEntities.Report.MesReport> GetListForReportTree(MESProductionDatabase database)
    {
    byte[] byteArray = new byte[1];
    var results =
        from report in database.MesReport
        select new { report.MesReportID, 
            report.ParentID, 
            report.ReportTitle, 
            report.ReportName, 
            report.DatabaseServer, 
            report.DatabaseName, 
            report.Login, 
            ReportFile = byteArray };

    return (List<L2SBusinessEntities.Report.MesReport>)results;
    }

I'm getting an unable to cast error in trying to cast 'results' to the type shown in the return statement. Should I be able to do this? An L2SBusinessEntities.Report.MesReport entity looks as follows:

int MesReportID
int ParentID
string ReportTitle
string ReportName
string DatabaseServer
string DatabaseName
string Login
byte[] ReportFile

Answer 1

Your method does not need casting. You can use the following code to return List of your objects:

public List<L2SBusinessEntities.Report.MesReport> GetListForReportTree(MESProductionDatabase database)
        {
        byte[] byteArray = new byte[1];
        var results = (
            from report in database.MesReport
            select new L2SBusinessEntities.Report.MesReport { 
                MesReportID = report.MesReportID, 
                ParentID = report.ParentID, 
                ReportTitle = report.ReportTitle, 
                ReportName = report.ReportName, 
                DatabaseServer = report.DatabaseServer, 
                DatabaseName = report.DatabaseName, 
                Login = report.Login, 
                ReportFile = byteArray }).ToList();

        return results;
        }

update -------------

another option for your query:

public List<L2SBusinessEntities.Report.MesReport> GetListForReportTree(MESProductionDatabase database)
        {
        byte[] byteArray = new byte[1];
        var results = (
            from report in database.MesReport
            select new { 
                MesReportID = report.MesReportID, 
                ParentID = report.ParentID, 
                ReportTitle = report.ReportTitle, 
                ReportName = report.ReportName, 
                DatabaseServer = report.DatabaseServer, 
                DatabaseName = report.DatabaseName, 
                Login = report.Login, 
                ReportFile = byteArray })
        .AsEnumerable()
        .Select(c => new L2SBusinessEntities.Report.MesReport{ 
                MesReportID = c.MesReportID, 
                ParentID = c.ParentID, 
                ReportTitle = c.ReportTitle, 
                ReportName = c.ReportName, 
                DatabaseServer = c.DatabaseServer, 
                DatabaseName = c.DatabaseName, 
                Login = c.Login, 
                ReportFile = c.ReportFile }).ToList();

        return results;
        }

Answer 2

change your code to something like:

....your code through "from report in database.MesReport" here
select new L2SBusinessEntities.Report.MesReport() {
  report.ParentID,   
  report.ReportTitle,   
  report.ReportName,   
  report.DatabaseServer,   
  report.DatabaseName,   
  report.Login,   
  ReportFile = byteArray 
};

If you wrap all of that in parens, you can then even call .ToList() on the LINQ query itself so you don't have to cast it when you return it.

Answer 3

Yeah, you cannot cast like that. You could add a constructor to your MesReport class that has params in the same order you listed to do this:

var results =
        from report in database.MesReport
        select new L2SBusinessEntities.Report.MesReport(report.MesReportID, 
            report.ParentID, 
            report.ReportTitle, 
            report.ReportName, 
            report.DatabaseServer, 
            report.DatabaseName, 
            report.Login, 
            ReportFile = byteArray);