NPOI 读写Excel

using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Text;
using System.Data;
using Microsoft.Win32;
using Microsoft.Windows.Controls;
using NPOI.HSSF.UserModel;
using NPOI.SS.UserModel;
using NPOI.XSSF.UserModel;


namespace LT.Utility
{
    /// <summary>
    /// FileName: NpoiExcelHelper.cs
    /// CLRVersion: 4.0.30319.18052
    /// Author: ZhangLei
    /// Corporation: Litu
    /// Description:Npoi Excel操作类封装
    /// DateTime: 2016/1/24 23:01:21
    /// </summary>
    public class NpoiExcelHelper
    {
        #region Public Interface

        /// <summary>
        /// 读取Excel到DataTable<see cref="System.Data.DataTable"/>
        /// </summary>
        /// <param name="file">Excel路径，如"E:\hello.xls"</param>
        /// <returns></returns>
        public static DataTable ExcelToTable(string file)
        {
            var type = GetFileType(file);
            if ( type== FileType.Excel2003)
            {
                return ExcelToTableForXLS(file);
            }
            else if (type == FileType.Excel2007)
            {
                return ExcelToTableForXLSX(file);
            }
            else
            {
                return null;
            }
        }

        /// <summary>
        /// DataTable 导出到 Excel
        /// </summary>
        /// <param name="dt"></param>
        public static void TableToExcel(DataTable dt)
        {
            SaveFileDialog saveFileDialog = new SaveFileDialog();
            saveFileDialog.Filter = "Excel 2003(*.xls)|*.xls|Excel 2007(*.xlsx)|*.xlsx";
            saveFileDialog.FilterIndex = 1;
            if (saveFileDialog.ShowDialog() == true)
            {
                if (saveFileDialog.FilterIndex == 1)
                {
                    TableToExcelForXLS(dt,saveFileDialog.FileName);
                }
                else
                {
                    TableToExcelForXLSX(dt, saveFileDialog.FileName);
                }
            }
        }

        /// <summary>
        /// DataTable 导出到 Excel
        /// </summary>
        /// <param name="dt"></param>
        /// <param name="file">Excel路径，如"E:\hello.xls"</param>
        public static void TableToExecel(DataTable dt, string file)
        {
            var type = GetFileType(file);
            if (type == FileType.Excel2003)
            {
                TableToExcelForXLS(dt, file);
            }
            else if (type == FileType.Excel2007)
            {
                TableToExcelForXLSX(dt, file);
            }
            else
            {
                throw new  Exception("暂不支持此种文件类型的输出");
            }
        }

        /// <summary>
        /// WPF DataGrid选中行数据导出到Excel
        /// </summary>
        /// <param name="dataGrid"></param>
        public static void SelectedRowToExcel(DataGrid dataGrid)
        {
            var dataView = dataGrid.ItemsSource as DataView;
            if (dataView != null)
            {
                DataTable dt = dataView.ToTable();
                dt.Rows.Clear();
                int sRowCount = dataGrid.SelectedItems.Count; 
                int col = dataGrid.Columns.Count;

                var sItems = dataGrid.SelectedItems;
                DataRow newRow = null;
                DataRowView drv = null;
                for (int i = 0; i < sRowCount; i++)
                {
                    newRow = dt.NewRow();
                    for (int j = 0; j < col; j++)
                    {
                        drv = sItems[i] as DataRowView;
                        newRow[j] = drv[j];
                    }
                    dt.Rows.Add(newRow);
                }
                TableToExcel(dt);
            }
            else
            {
                throw new Exception("DataGrid 数据源为null，无法导出到Excel");
            }
        }

        /// <summary>
        /// WPF DataGrid全部数据导出到Excel
        /// </summary>
        /// <param name="dataGrid"></param>
        public static void AllRowToExcel(DataGrid dataGrid)
        {
            var dataView = dataGrid.ItemsSource as DataView;
            if (dataView != null)
            {
                DataTable dt = dataView.ToTable();
                TableToExcel(dt);
            }
            else
            {
                throw new Exception("DataGrid 数据源为null，无法导出到Excel");
            }
        }
        #endregion

        #region Common Function

        private static FileType GetFileType(string file)
        {
            string extention = Path.GetExtension(file).ToLower();
           if(extention.Equals(".xls"))
            {
               return FileType.Excel2003;
            }
           else if (extention.Equals(".xlsx"))
           {
               return FileType.Excel2007;
           }
           else
           {
               return FileType.Other;
           }
        }

        enum FileType
        {
            Excel2003,
            Excel2007,
            Other
        }
        #endregion

        #region Excel2003
        /// <summary>  
        /// 将Excel文件中的数据读出到DataTable中(xls)  
        /// </summary>  
        /// <param name="file"></param>  
        /// <returns></returns>  
        private static DataTable ExcelToTableForXLS(string file)
        {
            DataTable dt = new DataTable();
            using (FileStream fs = new FileStream(file, FileMode.Open, FileAccess.Read))
            {

                HSSFWorkbook hssfworkbook = new HSSFWorkbook(fs);
                ISheet sheet = hssfworkbook.GetSheetAt(0);

                //表头  
                IRow header = sheet.GetRow(sheet.FirstRowNum);
                List<int> columns = new List<int>();
                for (int i = 0; i < header.LastCellNum; i++)
                {
                    object obj = GetValueTypeForXLS(header.GetCell(i) as HSSFCell);
                    if (obj == null || obj.ToString() == string.Empty)
                    {
                        dt.Columns.Add(new DataColumn("Columns" + i.ToString()));
                        //continue;  
                    }
                    else
                        dt.Columns.Add(new DataColumn(obj.ToString()));
                    columns.Add(i);
                }
                //数据  
                for (int i = sheet.FirstRowNum + 1; i <= sheet.LastRowNum; i++)
                {
                    DataRow dr = dt.NewRow();
                    bool hasValue = false;
                    foreach (int j in columns)
                    {
                        dr[j] = GetValueTypeForXLS(sheet.GetRow(i).GetCell(j) as HSSFCell);
                        if (dr[j] != null && dr[j].ToString() != string.Empty)
                        {
                            hasValue = true;
                        }
                    }
                    if (hasValue)
                    {
                        dt.Rows.Add(dr);
                    }
                }
            }
            return dt;
        }

        /// <summary>  
        /// 将DataTable数据导出到Excel文件中(xls)  
        /// </summary>  
        /// <param name="dt"></param>  
        /// <param name="file"></param>  
        private static void TableToExcelForXLS(DataTable dt, string file)
        {
            NPOI.HSSF.UserModel.HSSFWorkbook hssfworkbook = new NPOI.HSSF.UserModel.HSSFWorkbook();
            ISheet sheet = hssfworkbook.CreateSheet("Test");

            //表头  
            IRow row = sheet.CreateRow(0);
            for (int i = 0; i < dt.Columns.Count; i++)
            {
                ICell cell = row.CreateCell(i);
                cell.SetCellValue(dt.Columns[i].ColumnName);
            }

            //数据  
            for (int i = 0; i < dt.Rows.Count; i++)
            {
                IRow row1 = sheet.CreateRow(i + 1);
                for (int j = 0; j < dt.Columns.Count; j++)
                {
                    ICell cell = row1.CreateCell(j);
                    cell.SetCellValue(dt.Rows[i][j].ToString());
                }
            }

            //转为字节数组  
            MemoryStream stream = new MemoryStream();
            hssfworkbook.Write(stream);
            var buf = stream.ToArray();

            //保存为Excel文件  
            using (FileStream fs = new FileStream(file, FileMode.Create, FileAccess.Write))
            {
                fs.Write(buf, 0, buf.Length);
                fs.Flush();
            }
        }

        /// <summary>  
        /// 获取单元格类型(xls)  
        /// </summary>  
        /// <param name="cell"></param>  
        /// <returns></returns>  
        private static object GetValueTypeForXLS(HSSFCell cell)
        {
            if (cell == null)
                return null;
            switch (cell.CellType)
            {
                case CellType.Blank: //BLANK:  
                    return null;
                case CellType.Boolean: //BOOLEAN:  
                    return cell.BooleanCellValue;
                case CellType.Numeric: //NUMERIC:  
                    return cell.NumericCellValue;
                case CellType.String: //STRING:  
                    return cell.StringCellValue;
                case CellType.Error: //ERROR:  
                    return cell.ErrorCellValue;
                case CellType.Formula: //FORMULA:  
                default:
                    return "=" + cell.CellFormula;
            }
        }
        #endregion

        #region Excel2007及以上版本
        /// <summary>  
        /// 将Excel文件中的数据读出到DataTable中(xlsx)  
        /// </summary>  
        /// <param name="file"></param>  
        /// <returns></returns>  
        private static DataTable ExcelToTableForXLSX(string file)
        {
            DataTable dt = new DataTable();
            using (FileStream fs = new FileStream(file, FileMode.Open, FileAccess.Read))
            {
                //NPOI.XSSF.UserModel

                XSSFWorkbook xssfworkbook = new XSSFWorkbook(fs);
                ISheet sheet = xssfworkbook.GetSheetAt(0);

                //表头  
                IRow header = sheet.GetRow(sheet.FirstRowNum);
                List<int> columns = new List<int>();
                for (int i = 0; i < header.LastCellNum; i++)
                {
                    object obj = GetValueTypeForXLSX(header.GetCell(i) as XSSFCell);
                    if (obj == null || obj.ToString() == string.Empty)
                    {
                        dt.Columns.Add(new DataColumn("Columns" + i.ToString()));
                        //continue;  
                    }
                    else
                        dt.Columns.Add(new DataColumn(obj.ToString()));
                    columns.Add(i);
                }
                //数据  
                for (int i = sheet.FirstRowNum + 1; i <= sheet.LastRowNum; i++)
                {
                    DataRow dr = dt.NewRow();
                    bool hasValue = false;
                    foreach (int j in columns)
                    {
                        dr[j] = GetValueTypeForXLSX(sheet.GetRow(i).GetCell(j) as XSSFCell);
                        if (dr[j] != null && dr[j].ToString() != string.Empty)
                        {
                            hasValue = true;
                        }
                    }
                    if (hasValue)
                    {
                        dt.Rows.Add(dr);
                    }
                }
            }
            return dt;
        }

        /// <summary>  
        /// 将DataTable数据导出到Excel文件中(xlsx)  
        /// </summary>  
        /// <param name="dt"></param>  
        /// <param name="file"></param>  
        private static void TableToExcelForXLSX(DataTable dt, string file)
        {

            XSSFWorkbook xssfworkbook = new XSSFWorkbook();
            ISheet sheet = xssfworkbook.CreateSheet("Test");

            //表头  
            IRow row = sheet.CreateRow(0);
            for (int i = 0; i < dt.Columns.Count; i++)
            {
                ICell cell = row.CreateCell(i);
                cell.SetCellValue(dt.Columns[i].ColumnName);
            }

            //数据  
            for (int i = 0; i < dt.Rows.Count; i++)
            {
                IRow row1 = sheet.CreateRow(i + 1);
                for (int j = 0; j < dt.Columns.Count; j++)
                {
                    ICell cell = row1.CreateCell(j);
                    cell.SetCellValue(dt.Rows[i][j].ToString());
                }
            }

            //转为字节数组  
            MemoryStream stream = new MemoryStream();
            xssfworkbook.Write(stream);
            var buf = stream.ToArray();

            //保存为Excel文件  
            using (FileStream fs = new FileStream(file, FileMode.Create, FileAccess.Write))
            {
                fs.Write(buf, 0, buf.Length);
                fs.Flush();
            }
        }

        /// <summary>  
        /// 获取单元格类型(xlsx)  
        /// </summary>  
        /// <param name="cell"></param>  
        /// <returns></returns>  
        private static object GetValueTypeForXLSX(XSSFCell cell)
        {
            if (cell == null)
                return null;
            switch (cell.CellType)
            {
                case CellType.Blank: //BLANK:  
                    return null;
                case CellType.Boolean: //BOOLEAN:  
                    return cell.BooleanCellValue;
                case CellType.Numeric: //NUMERIC:  
                    return cell.NumericCellValue;
                case CellType.String: //STRING:  
                    return cell.StringCellValue;
                case CellType.Error: //ERROR:  
                    return cell.ErrorCellValue;
                case CellType.Formula: //FORMULA:  
                default:
                    return "=" + cell.CellFormula;
            }
        }
        #endregion
        
    }  

}