how to resolve 'DataSet does not support System.Nullable<>.'? - asp.net

Question

My goal is to export data to a pdf file using crystal report and entity framework but unfortunately, I have been receiving this error message when I try to run my code.
'System.NotSupportedException: 'DataSet does not support System.Nullable<>.'
Can anyone please kindly assist me?
This is what I have tried so far on my controller side
using System.Data.Entity;
using System.IO;
using Final_INF271.Reports;
using CrystalDecisions.CrystalReports.Engine;
public ActionResult Export()
{
ReportDocument rd = new ReportDocument();
rd.Load(Path.Combine(Server.MapPath("~/Reports/OutstandingOrders.rpt")));
rd.SetDataSource(db.ProductOrder.Select(p => new
{
p.OrderID,
p.Date,
p.SupplierID,
p.CostPrice,
p.Quantity
}).ToList());
Response.Buffer = false;
Response.ClearContent();
Response.ClearHeaders();
Stream stream = rd.ExportToStream
(CrystalDecisions.Shared.ExportFormatType.PortableDocFormat);
stream.Seek(0, SeekOrigin.Begin);
return File(stream, "application/pdf", "OutstandingOrders");
}
Included is my ProductOrder
namespace Final_INF271.Models
{
using System;
using System.Collections.Generic;
public partial class ProductOrder
{
public int OrderID { get; set; }
public Nullable<System.DateTime> Date { get; set; }
public Nullable<int> EmployeeID { get; set; }
public Nullable<int> SupplierID { get; set; }
public int ProductTypeID { get; set; }
public Nullable<decimal> CostPrice { get; set; }
public Nullable<int> Quantity { get; set; }
public virtual Employee Employee { get; set; }
public virtual ProductType ProductType { get; set; }
public virtual Supplier Supplier { get; set; }
}
}
below is a picture of Data set and error message

Answer 1

Crystal Reports' SetDataSource() method creates DataColumn supplied by list of ProductOrder, and then trying to build DataColumn instances that has nullable type, which is not supported.
You should either create a viewmodel class which has properties with same base types but without nullable types present, then project the result with that class as data source:
// Viewmodel
public class ProductOrderVM
{
public int OrderID { get; set; }
public DateTime Date { get; set; }
public int SupplierID { get; set; }
public decimal CostPrice { get; set; }
public int Quantity { get; set; }
}
// Controller action
rd.SetDataSource(db.ProductOrder.Select(p => new ProductOrderVM
{
OrderID = p.OrderID,
Date = p.Date.GetValueOrDefault(),
SupplierID = p.SupplierID.GetValueOrDefault(),
CostPrice = p.CostPrice.GetValueOrDefault(),
Quantity = p.Quantity.GetValueOrDefault()
}).ToList());
Or use null coalescing/ternary operator to assign default values according to their base type if the nullable properties have null value:
rd.SetDataSource(db.ProductOrder.Select(p => new
{
OrderID = p.OrderID,
// with ternary operator
Date = p.Date == null ? DateTime.MinValue : p.Date, // or DateTime.Now as default value
// with null-coalescing operator
SupplierID = p.SupplierID ?? 0,
CostPrice = p.CostPrice ?? 0,
Quantity = p.Quantity ?? 0
}).ToList());