使用VS 2015和MVC5进行Crystal报表

Question

我是MVC5的新手，使用Crystal报表工具时出现此错误

  

发生了'System.NotSupportedException'类型的异常   System.Data.dll但未在用户代码中处理

     

其他信息：'DataSet'不支持System.Nullable＆lt;＆gt;。

using CrystalDecisions.CrystalReports.Engine;
using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Web;
using System.Web.Mvc;

namespace CrystalReportMVC.Controllers
{
    public class CustomerController : Controller
    {
        //DbContext  
        private CustomerDBEntities context = new CustomerDBEntities();
        // GET: Customer  
        public ActionResult Index()
        {
            var customerList = context.Customers.ToList();
            return View(customerList);
        }


        public ActionResult ExportCustomers()
        {
            List<Customer> allCustomer = new List<Customer>();
            allCustomer = context.Customers.ToList();


            ReportDocument rd = new ReportDocument();
            rd.Load(Path.Combine(Server.MapPath("~/CrystalReports"), "ReportCustomer.rpt"));

            rd.SetDataSource(allCustomer);

            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", "CustomerList.pdf");
        }

    }
}`