Export data to excel with EPPlus and Web Api - HELP!

Question

I am trying to do a simple excel file export with EPPlus and Web Api. In the html client I have a button that calls the web api and opens a new window. No error is thrown, but the result is always "file could not be downloaded".  I get the
save file dialog but the file name is Order/ instead of the expected Orders.xls or Orders.xlsx.  Can anyone help? I'm surprised this is so difficult.
using System.Linq;
using System.Net.Http;
using System.Web.Http;
using OfficeOpenXml;
using System.Collections.Generic;
using System.IO;
using System.Net.Http.Headers;
using System.Net;
using System.ComponentModel.DataAnnotations;
namespace LightSwitchApplication
public class OrdersController : ApiController
// GET: api/Orders
[HttpGet]
public HttpResponseMessage Get()
HttpResponseMessage response;
response = Request.CreateResponse(HttpStatusCode.OK);
MediaTypeHeaderValue mediaType = new MediaTypeHeaderValue("application/octet-stream");
response.Content = new StreamContent(GetExcelSheet());
response.Content.Headers.ContentType = mediaType;
response.Content.Headers.ContentDisposition = new ContentDispositionHeaderValue("attachment");
response.Content.Headers.ContentDisposition.FileName = "Orders.xls";
return response;
public List<Order> GetOrders()
List<Order> colOrders = new List<Order>();
using (ServerApplicationContext ctx = ServerApplicationContext.Current ??
ServerApplicationContext.CreateContext())
colOrders = ctx.DataWorkspace.Data.Orders.GetQuery().Execute().ToList();
return colOrders;
public MemoryStream GetExcelSheet()
using (var package = new ExcelPackage())
var worksheet = package.Workbook.Worksheets.Add("Orders");
worksheet.Cells["A1"].LoadFromCollection(GetOrders(), false);
package.Save();
var stream = new MemoryStream(package.GetAsByteArray());
return stream;
This has been driving me crazy for two days!

Answer 1

Making some progress.  I got the spreadsheet into a byte[] and used code from Paul Van
Bladel's blog to make the HttpResponseMessage.  If I comment out the LightSwitch data access code, this works to export a spreadsheet from a static list to the browser from Web Api.
using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Net;
using System.Net.Http;
using System.Net.Http.Headers;
using System.Web.Http;
using Microsoft.LightSwitch;
using Microsoft.LightSwitch.Details;
using OfficeOpenXml;
using System.ComponentModel.DataAnnotations;
namespace LightSwitchApplication
public class Order
[Key]
public int Id { get; set; }
public string OrderNumber { get; set; }
public class OrdersController : ApiController
// GET: api/Orders
[HttpGet]
public HttpResponseMessage Download()
MediaTypeHeaderValue mediaType =
MediaTypeHeaderValue.Parse("application/octet-stream");
byte[] excelFile = ExcelSheet();
string fileName = "Orders.xlsx";
MemoryStream memoryStream = new MemoryStream(excelFile);
HttpResponseMessage response =
response = Request.CreateResponse(HttpStatusCode.OK);
response.Content = new StreamContent(memoryStream);
response.Content.Headers.ContentType = mediaType;
response.Content.Headers.ContentDisposition =
new ContentDispositionHeaderValue("fileName") { FileName = fileName };
return response;
public List<Order> Orders()
List<Order> orders = new List<Order>();
orders.Add(new Order { Id = 1, OrderNumber = "123456789" });
orders.Add(new Order { Id = 2, OrderNumber = "987654321" });
return orders;
// this doesn't work
//public List<Order> Orders()
// List<Order> colOrders = new List<Order>();
// using (ServerApplicationContext ctx = ServerApplicationContext.Current ??
// ServerApplicationContext.CreateContext())
// colOrders = ctx.DataWorkspace.Data.Orders.GetQuery().Execute().ToList();
// return colOrders;
public byte[] ExcelSheet()
using (var package = new ExcelPackage())
var worksheet = package.Workbook.Worksheets.Add("Orders");
worksheet.Cells["A1"].LoadFromCollection(Orders(), false);
byte[] bytes = package.GetAsByteArray();
return bytes;
The problem is that the LightSwitch query (commented out in the code above) is trying to load navigation properties for the orders.  Error: "It is not valid to access this object on the current thread."  How do I solve this?