title: how to resolve 'DataSet does not support System.Nullable<>.'?
body: <p>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.</p>
  
  <blockquote>
    <p>'System.NotSupportedException: 'DataSet does not support System.Nullable&lt;>.'</p>
  </blockquote>
  
  <p>Can anyone please kindly assist me?</p>
  
  <p>This is what I have tried so far on my controller side</p>
  
  <pre><code>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 =&gt; 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");
  }
  </code></pre>
  
  <p>Included is my ProductOrder</p>
  
  <pre><code>namespace Final_INF271.Models
  {
      using System;
      using System.Collections.Generic;
  
      public partial class ProductOrder
      {
          public int OrderID { get; set; }
          public Nullable&lt;System.DateTime&gt; Date { get; set; }
          public Nullable&lt;int&gt; EmployeeID { get; set; }
          public Nullable&lt;int&gt; SupplierID { get; set; }
          public int ProductTypeID { get; set; }
          public Nullable&lt;decimal&gt; CostPrice { get; set; }
          public Nullable&lt;int&gt; Quantity { get; set; }
  
          public virtual Employee Employee { get; set; }
          public virtual ProductType ProductType { get; set; }
          public virtual Supplier Supplier { get; set; }
      }
  }
  </code></pre>
  
  <p>below is a picture of Data set and error message</p>
  
  <p><a href="https://i.stack.imgur.com/bRhPM.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/bRhPM.png" alt="enter image description here"></a></p>