ExportHelper.cs

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using OfficeOpenXml;
using OfficeOpenXml.Style;

namespace ExcelExport
{
    public static class ExcelExportHelper
    {
        public static string ExcelContentType => "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet";

        public static DataTable ListToDataTable<T>(List<T> data)
        {
            PropertyDescriptorCollection properties = TypeDescriptor.GetProperties(typeof(T));
            DataTable dataTable = new DataTable();

            for (int i = 0; i < properties.Count; i++)
            {
                PropertyDescriptor property = properties[i];
                dataTable.Columns.Add(property.Name, Nullable.GetUnderlyingType(property.PropertyType) ?? property.PropertyType);
            }

            object[] values = new object[properties.Count];
            foreach (T item in data)
            {
                for (int i = 0; i < values.Length; i++)
                {
                    values[i] = properties[i].GetValue(item);
                }

                dataTable.Rows.Add(values);
            }
            return dataTable;
        }

        public static byte[] ExportExcel(DataTable dataTable, string heading = "", bool showSrNo = false, params string[] columnsToTake)
        {
            byte[] result = null;
            using (ExcelPackage package = new ExcelPackage())
            {
                ExcelWorksheet workSheet = package.Workbook.Worksheets.Add(String.Format("{0} Data", heading));
                workSheet.View.RightToLeft = true;
                int startRowFrom = String.IsNullOrEmpty(heading) ? 1 : 3;

                if (showSrNo)
                {
                    DataColumn dataColumn = dataTable.Columns.Add("#", typeof(int));
                    dataColumn.SetOrdinal(0);
                    int index = 1;
                    foreach (DataRow item in dataTable.Rows)
                    {
                        item[0] = index;
                        index++;
                    }
                }

                // add the content into the Excel file  
                workSheet.Cells["A" + startRowFrom].LoadFromDataTable(dataTable, true);
                // format header - bold, yellow on black  
                using (ExcelRange r = workSheet.Cells[startRowFrom, 1, startRowFrom, dataTable.Columns.Count])
                {
                    r.Style.Font.Color.SetColor(System.Drawing.Color.White);
                    r.Style.Font.Bold = true;
                    r.Style.Fill.PatternType = OfficeOpenXml.Style.ExcelFillStyle.Solid;
                    r.Style.Fill.BackgroundColor.SetColor(System.Drawing.ColorTranslator.FromHtml("#1fb5ad"));
                }

                // format cells - add borders  
                using (ExcelRange r = workSheet.Cells[startRowFrom + 1, 1, startRowFrom + dataTable.Rows.Count, dataTable.Columns.Count])
                {
                    r.Style.Border.Top.Style = ExcelBorderStyle.Thin;
                    r.Style.Border.Bottom.Style = ExcelBorderStyle.Thin;
                    r.Style.Border.Left.Style = ExcelBorderStyle.Thin;
                    r.Style.Border.Right.Style = ExcelBorderStyle.Thin;

                    r.Style.Border.Top.Color.SetColor(System.Drawing.Color.Black);
                    r.Style.Border.Bottom.Color.SetColor(System.Drawing.Color.Black);
                    r.Style.Border.Left.Color.SetColor(System.Drawing.Color.Black);
                    r.Style.Border.Right.Color.SetColor(System.Drawing.Color.Black);
                }

                if (!String.IsNullOrEmpty(heading))
                {
                    workSheet.Cells["A1"].Value = heading;
                    workSheet.Cells["A1"].Style.Font.Size = 20;

                    workSheet.InsertColumn(1, 1);
                    workSheet.InsertRow(1, 1);
                    workSheet.Column(1).Width = 5;
                }

                result = package.GetAsByteArray();
            }

            return result;
        }

        public static byte[] ExportExcel<T>(List<T> data, string Heading = "", bool showSlno = false, params string[] ColumnsToTake)
        {
            return ExportExcel(ListToDataTable<T>(data), Heading, showSlno, ColumnsToTake);
        }
    }
}