根据Excel列类型获取列的值

using System.Data;
using System.IO;
using System.Text;
using System.Web;
using NPOI.SS.UserModel;
using NPOI.HSSF.UserModel;

namespace AIMSCommon
{
    public class ExcelRender
    {
        /// <summary>
        /// 根据Excel列类型获取列的值
        /// </summary>
        /// <param name="cell">Excel列</param>
        /// <returns></returns>
        private static string GetCellValue(ICell cell)
        {
            if (cell == null)
                return string.Empty;
            switch (cell.CellType)
            {
                case CellType.BLANK:
                    return string.Empty;
                case CellType.BOOLEAN:
                    return cell.BooleanCellValue.ToString();
                case CellType.ERROR:
                    return cell.ErrorCellValue.ToString();
                case CellType.NUMERIC:
                case CellType.Unknown:
                default:
                    return cell.ToString();
                case CellType.STRING:
                    return cell.StringCellValue;
                case CellType.FORMULA:
                    try
                    {
                        HSSFFormulaEvaluator e = new HSSFFormulaEvaluator(cell.Sheet.Workbook);
                        e.EvaluateInCell(cell);
                        return cell.ToString();
                    }
                    catch
                    {
                        return cell.NumericCellValue.ToString();
                    }
            }
        }

        /// <summary>
        /// 自动设置Excel列宽
        /// </summary>
        /// <param name="sheet">Excel表</param>
        private static void AutoSizeColumns(ISheet sheet)
        {
            if (sheet.PhysicalNumberOfRows > 0)
            {
                IRow headerRow = sheet.GetRow(0);

                for (int i = 0, l = headerRow.LastCellNum; i < l; i++)
                {
                    sheet.AutoSizeColumn(i);
                }
            }
        }

        /// <summary>
        /// 保存Excel文档流到文件
        /// </summary>
        /// <param name="ms">Excel文档流</param>
        /// <param name="fileName">文件名</param>
        private static void SaveToFile(MemoryStream ms, string fileName)
        {
            using (FileStream fs = new FileStream(fileName, FileMode.Create, FileAccess.Write))
            {
                byte[] data = ms.ToArray();

                fs.Write(data, 0, data.Length);
                fs.Flush();

                data = null;
            }
        }

        /// <summary>
        /// 输出文件到浏览器
        /// </summary>
        /// <param name="ms">Excel文档流</param>
        /// <param name="context">HTTP上下文</param>
        /// <param name="fileName">文件名</param>
        private static void RenderToBrowser(MemoryStream ms, HttpContext context, string fileName)
        {
            if (context.Request.Browser.Browser == "IE")
                fileName = HttpUtility.UrlEncode(fileName);
            context.Response.AddHeader("Content-Disposition", "attachment;fileName=" + fileName);
            context.Response.BinaryWrite(ms.ToArray());
        }

        /// <summary>
        /// DataTable转换成Excel文档流
        /// </summary>
        /// <param name="table"></param>
        /// <returns></returns>
        public static MemoryStream RenderToExcel(DataTable table)
        {
            MemoryStream ms = new MemoryStream();
            using (table)
            {
                using (IWorkbook workbook = new HSSFWorkbook())
                {
                    using (ISheet sheet = workbook.CreateSheet())
                    {
                        IRow headerRow = sheet.CreateRow(0);
                        foreach (DataColumn column in table.Columns)
                            headerRow.CreateCell(column.Ordinal).SetCellValue(column.Caption);
                        int rowIndex = 1;
                        foreach (DataRow row in table.Rows)
                        {
                            IRow dataRow = sheet.CreateRow(rowIndex);
                            foreach (DataColumn column in table.Columns)
                            {
                                dataRow.CreateCell(column.Ordinal).SetCellValue(row[column].ToString());
                            }
                            rowIndex++;
                        }
                        AutoSizeColumns(sheet);
                        workbook.Write(ms);
                        ms.Flush();
                        ms.Position = 0;
                    }
                }
            }
            return ms;
        }

        /// <summary>
        /// DataTable转换成Excel文档流，并保存到文件
        /// </summary>
        /// <param name="table"></param>
        /// <param name="fileName">保存的路径</param>
        public static void RenderToExcel(DataTable table, string fileName)
        {
            using (MemoryStream ms = RenderToExcel(table))
            {
                SaveToFile(ms, fileName);
            }
        }

        /// <summary>
        /// DataTable转换成Excel文档流，并输出到客户端
        /// </summary>
        /// <param name="table"></param>
        /// <param name="response"></param>
        /// <param name="fileName">输出的文件名</param>
        public static void RenderToExcel(DataTable table, HttpContext context, string fileName)
        {
            using (MemoryStream ms = RenderToExcel(table))
            {
                RenderToBrowser(ms, context, fileName);
            }
        }

        /// <summary>
        /// Excel文档流是否有数据
        /// </summary>
        /// <param name="excelFileStream">Excel文档流</param>
        /// <returns></returns>
        public static bool HasData(Stream excelFileStream)
        {
            return HasData(excelFileStream, 0);
        }

        /// <summary>
        /// Excel文档流是否有数据
        /// </summary>
        /// <param name="excelFileStream">Excel文档流</param>
        /// <param name="sheetIndex">表索引号，如第一个表为0</param>
        /// <returns></returns>
        public static bool HasData(Stream excelFileStream, int sheetIndex)
        {
            using (excelFileStream)
            {
                using (IWorkbook workbook = new HSSFWorkbook(excelFileStream))
                {
                    if (workbook.NumberOfSheets > 0)
                    {
                        if (sheetIndex < workbook.NumberOfSheets)
                        {
                            using (ISheet sheet = workbook.GetSheetAt(sheetIndex))
                            {
                                return sheet.PhysicalNumberOfRows > 0;
                            }
                        }
                    }
                }
            }
            return false;
        }

        /// <summary>
        /// Excel文档流转换成DataTable
        /// 第一行必须为标题行
        /// </summary>
        /// <param name="excelFileStream">Excel文档流</param>
        /// <param name="sheetName">表名称</param>
        /// <returns></returns>
        public static DataTable RenderFromExcel(Stream excelFileStream, string sheetName)
        {
            return RenderFromExcel(excelFileStream, sheetName, 0);
        }

        /// <summary>
        /// Excel文档流转换成DataTable
        /// </summary>
        /// <param name="excelFileStream">Excel文档流</param>
        /// <param name="sheetName">表名称</param>
        /// <param name="headerRowIndex">标题行索引号，如第一行为0</param>
        /// <returns></returns>
        public static DataTable RenderFromExcel(Stream excelFileStream, string sheetName, int headerRowIndex)
        {
            DataTable table = null;

            using (excelFileStream)
            {
                using (IWorkbook workbook = new HSSFWorkbook(excelFileStream))
                {
                    using (ISheet sheet = workbook.GetSheet(sheetName))
                    {
                        table = RenderFromExcel(sheet, headerRowIndex);
                    }
                }
            }
            return table;
        }

        /// <summary>
        /// Excel文档流转换成DataTable
        /// 默认转换Excel的第一个表
        /// 第一行必须为标题行
        /// </summary>
        /// <param name="excelFileStream">Excel文档流</param>
        /// <returns></returns>
        public static DataTable RenderFromExcel(Stream excelFileStream)
        {
            return RenderFromExcel(excelFileStream, 0, 0);
        }

        /// <summary>
        /// Excel文档流转换成DataTable
        /// 第一行必须为标题行
        /// </summary>
        /// <param name="excelFileStream">Excel文档流</param>
        /// <param name="sheetIndex">表索引号，如第一个表为0</param>
        /// <returns></returns>
        public static DataTable RenderFromExcel(Stream excelFileStream, int sheetIndex)
        {
            return RenderFromExcel(excelFileStream, sheetIndex, 0);
        }

        /// <summary>
        /// Excel文档流转换成DataTable
        /// </summary>
        /// <param name="excelFileStream">Excel文档流</param>
        /// <param name="sheetIndex">表索引号，如第一个表为0</param>
        /// <param name="headerRowIndex">标题行索引号，如第一行为0</param>
        /// <returns></returns>
        public static DataTable RenderFromExcel(Stream excelFileStream, int sheetIndex, int headerRowIndex)
        {
            DataTable table = null;

            using (excelFileStream)
            {
                using (IWorkbook workbook = new HSSFWorkbook(excelFileStream))
                {
                    using (ISheet sheet = workbook.GetSheetAt(sheetIndex))
                    {
                        table = RenderFromExcel(sheet, headerRowIndex);
                    }
                }
            }
            return table;
        }

        /// <summary>
        /// Excel表格转换成DataTable
        /// </summary>
        /// <param name="sheet">表格</param>
        /// <param name="headerRowIndex">标题行索引号，如第一行为0</param>
        /// <returns></returns>
        private static DataTable RenderFromExcel(ISheet sheet, int headerRowIndex)
        {
            DataTable table = new DataTable();

            IRow headerRow = sheet.GetRow(headerRowIndex);
            int cellCount = headerRow.LastCellNum;//LastCellNum = PhysicalNumberOfCells
            int rowCount = sheet.LastRowNum;//LastRowNum = PhysicalNumberOfRows - 1

            //handling header.
            for (int i = headerRow.FirstCellNum; i < cellCount; i++)
            {
                DataColumn column = new DataColumn(headerRow.GetCell(i).StringCellValue);
                table.Columns.Add(column);
            }

            for (int i = (sheet.FirstRowNum + 1); i <= rowCount; i++)
            {
                IRow row = sheet.GetRow(i);
                DataRow dataRow = table.NewRow();

                if (row != null)
                {
                    for (int j = row.FirstCellNum; j < cellCount; j++)
                    {
                        if (row.GetCell(j) != null)
                            dataRow[j] = GetCellValue(row.GetCell(j));
                    }
                }

                table.Rows.Add(dataRow);
            }

            return table;
        }
    }
}