I'm trying to set the DataSource for a Crystal Reports report, but I've run into a few problems. I've been following a guide written by Mohammad Mahdi Ramezanpour, and have managed to get all the way to the last part now (setting the DataSource). However, I have a problem that Mohammad does not seem to have - when I pass the results of my query to the report, I end up with the following exception:

DataSet does not support System.Nullable<>

This is the query I am using:

public IQueryable<Part> GetPartsToDisplayOnStockReport()
{
    return from part in db.Parts
           where part.showOnStockReport == true
           select part;
}

and the way I pass it to the Report:

public ActionResult ViewStockReport()
{
    StockReport stockReport = new StockReport();
    var parts = ordersRepository.GetPartsToDisplayOnStockReport().ToList();
    stockReport.SetDataSource(parts);

    Stream stream = stockReport.ExportToStream(CrystalDecisions.Shared.ExportFormatType.PortableDocFormat);
    return File(stream, "application/pdf");
}

I have also tried changing my query to this code, in the hope that it would fix my problem:

return (from part in db.Parts
       where part.showOnStockReport == true
       select part) ?? db.Parts.DefaultIfEmpty();

but it still complained about the same problem.

How can I pass the results of this query to my report, to use it as a data source? Also, if each of my Parts object contains other objects / collections of other objects, will I be able to reference them in the report with a datasource like this?