Export items to an excel spreadsheet

ExcelExportTool.cs

using System;
using System.Collections.Generic;
using System.Data;
using System.Reflection;
using OfficeOpenXml;
using OfficeOpenXml.Table;

namespace Utils
{
    public static class ExcelExportTool
    {
        public static readonly string ContentType = "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet";

        public static byte[] GetReport<T>(string worksheetName, IEnumerable<T> items)
        {
            var table = ToDataTable(items);

            using (var package = new ExcelPackage())
            {
                var worksheet = package.Workbook.Worksheets.Add(worksheetName);
                worksheet.Cells.LoadFromDataTable(table, true, TableStyles.Light8);
                return package.GetAsByteArray();
            }
        }

        private static DataTable ToDataTable<T>(IEnumerable<T> entityList)
        {
            var dtReturn = new DataTable();

            // column names
            PropertyInfo[] oProps = null;

            if (entityList == null) return dtReturn;

            foreach (var rec in entityList)
            {
                // Use reflection to get property names, to create table, Only first time, others will follow
                if (oProps == null)
                {
                    oProps = rec.GetType().GetProperties();
                    foreach (var pi in oProps)
                    {
                        var colType = pi.PropertyType;

                        if ((colType.IsGenericType) && (colType.GetGenericTypeDefinition() == typeof (Nullable<>)))
                        {
                            colType = colType.GetGenericArguments()[0];
                        }

                        dtReturn.Columns.Add(new DataColumn(pi.Name, colType));
                    }
                }

                var dr = dtReturn.NewRow();

                foreach (var pi in oProps)
                {
                    dr[pi.Name] = pi.GetValue(rec, null) ?? DBNull.Value;
                }

                dtReturn.Rows.Add(dr);
            }
            return dtReturn;
        }
    }
}

Sample usage in a controller

    // GET: /Items/Export
    public ActionResult Export()
    {
        var items= GetAllItems();
        var excel = ExcelExportTool.GetReport("Items", items);
        var fileName = string.Format("Items_report_{0}.xlsx", DateTime.Now.ToString("dd-MMM-yy-HHmm"));
        return File(excel, ExcelExportTool.ContentType, fileName);
    }

Note: requires lib from nuget Install-Package EPPlus, see http://epplus.codeplex.com/