C#-读写Excel学习笔记

一、C#读写Excel的几种方法

二、C#读写Excel-Microsoft.Office.Interop.Excel

前提是本机须安装office才能运行，且不同的office版本之间可能会有兼容问题，从Nuget下载 Microsoft.Office.Interop.Excel。

三、NPOI方法（推荐、在不安装office的时候也是可以读写的，速度很快）：

1、Excel与DataTable转换：

/**
*┌──────────────────────────────────────────────────────────────┐
*│　描    述：EXCEL操作类                                              
*│　作    者：执笔小白                                              
*│　版    本：1.0                                       
*│　创建时间：2020-11-26 10:16                         
*└──────────────────────────────────────────────────────────────┘
*┌──────────────────────────────────────────────────────────────┐
*│　命名空间: Util                               
*│　类    名：NPOIHelper                                    
*└──────────────────────────────────────────────────────────────┘
*/
 using NPOI.HSSF.UserModel;
 using NPOI.XSSF.UserModel;
 using System;
 using System.Data;
 using System.IO;
 
 /// <summary>
 /// EXCEL操作类
 /// </summary>
 public class NPOIHelper
 {
     /// <summary>
     /// 读取Excel文件到DataTable
     /// </summary>
     /// <param name="filePath"></param>
     /// <returns></returns>
     public static DataTable ReadExcel(string filePath)
     {
         NPOI.SS.UserModel.ISheet sheet;
         if (filePath.Contains(".xlsx"))  // 2007 xlsx
         {
             #region//初始化信息
             XSSFWorkbook hssfworkbook;
             try
             {
                 using (FileStream file = new FileStream(filePath, FileMode.Open, FileAccess.Read))
                 {
                     hssfworkbook = new XSSFWorkbook(file);
                 }
             }
             catch (Exception e)
             {
                 throw e;
             }
             sheet = hssfworkbook.GetSheetAt(0);
             #endregion
             System.Collections.IEnumerator rows = sheet.GetRowEnumerator();
             DataTable dt = new DataTable();
             for (int j = 0; j < (sheet.GetRow(0).LastCellNum); j++)  // cell数
             {
                 dt.Columns.Add(Convert.ToChar(((int)'A') + j).ToString());
             }
             while (rows.MoveNext())
             {
                 XSSFRow row = (XSSFRow)rows.Current;
                 DataRow dr = dt.NewRow();
                 for (int i = 0; i < row.LastCellNum; i++)
                 {
                     NPOI.SS.UserModel.ICell cell = row.GetCell(i);
                     if (cell == null)
                     {
                         dr[i] = null;
                     }
                     else
                     {
                         dr[i] = cell.ToString();
                     }
                 }
                 dt.Rows.Add(dr);
             }
             return dt;
         }
         else  // 2003 xls
         {
             HSSFWorkbook hssfworkbook;
             try
             {
                 using (FileStream file = new FileStream(filePath, FileMode.Open, FileAccess.Read))
                 {
                     hssfworkbook = new HSSFWorkbook(file);
                 }
             }
             catch (Exception e)
             {
                 throw e;
             }
             sheet = hssfworkbook.GetSheetAt(0);
             System.Collections.IEnumerator rows = sheet.GetRowEnumerator();
             DataTable dt = new DataTable();
             for (int j = 0; j < (sheet.GetRow(0).LastCellNum); j++)
             {
                 dt.Columns.Add(Convert.ToChar(((int)'A') + j).ToString());
             }
             while (rows.MoveNext())
             {
                 HSSFRow row = (HSSFRow)rows.Current;
                 DataRow dr = dt.NewRow();
                 for (int i = 0; i < row.LastCellNum; i++)
                 {
                     NPOI.SS.UserModel.ICell cell = row.GetCell(i);
                     if (cell == null)
                     {
                         dr[i] = null;
                     }
                     else
                     {
                         dr[i] = cell.ToString();
                     }
                 }
                 dt.Rows.Add(dr);
             }
             return dt;
         }
     }
 
     /// <summary>
     /// 将DataTable数据写入Excel文件
     /// </summary>
     /// <param name="dt"></param>
     /// <param name="filePath"></param>
     public static void WriteExcel(DataTable dt, string filePath)
     {
         if (!string.IsNullOrEmpty(filePath) && null != dt && dt.Rows.Count > 0)
         {
             if (filePath.Contains(".xlsx"))  //  2007 xlsx
             {
                 XSSFWorkbook book = new XSSFWorkbook();
                 NPOI.SS.UserModel.ISheet sheet = book.CreateSheet(dt.TableName);
 
                 NPOI.SS.UserModel.IRow row = sheet.CreateRow(0);
                 for (int i = 0; i < dt.Columns.Count; i++)
                 {
                     row.CreateCell(i).SetCellValue(dt.Columns[i].ColumnName);
                 }
                 for (int i = 0; i < dt.Rows.Count; i++)
                 {
                     NPOI.SS.UserModel.IRow row2 = sheet.CreateRow(i + 1);
                     for (int j = 0; j < dt.Columns.Count; j++)
                     {
                         row2.CreateCell(j).SetCellValue(Convert.ToString(dt.Rows[i][j]));
                     }
                 }
                 // 写入到客户端  
                 using (System.IO.MemoryStream ms = new System.IO.MemoryStream())
                 {
                     book.Write(ms);
                     using (FileStream fs = new FileStream(filePath, FileMode.Create, FileAccess.Write))
                     {
                         byte[] data = ms.ToArray();
                         fs.Write(data, 0, data.Length);
                         fs.Flush();
                     }
                     book = null;
                 }
             }
             else  // 2003 xls
             {
                 NPOI.HSSF.UserModel.HSSFWorkbook book = new NPOI.HSSF.UserModel.HSSFWorkbook();
                 NPOI.SS.UserModel.ISheet sheet = book.CreateSheet(dt.TableName);
 
                 NPOI.SS.UserModel.IRow row = sheet.CreateRow(0);
                 for (int i = 0; i < dt.Columns.Count; i++)
                 {
                     row.CreateCell(i).SetCellValue(dt.Columns[i].ColumnName);
                 }
                 for (int i = 0; i < dt.Rows.Count; i++)
                 {
                     NPOI.SS.UserModel.IRow row2 = sheet.CreateRow(i + 1);
                     for (int j = 0; j < dt.Columns.Count; j++)
                     {
                         row2.CreateCell(j).SetCellValue(Convert.ToString(dt.Rows[i][j]));
                     }
                 }
                 // 写入到客户端  
                 using (System.IO.MemoryStream ms = new System.IO.MemoryStream())
                 {
                     book.Write(ms);
                     using (FileStream fs = new FileStream(filePath, FileMode.Create, FileAccess.Write))
                     {
                         byte[] data = ms.ToArray();
                         fs.Write(data, 0, data.Length);
                         fs.Flush();
                     }
                     book = null;
                 }
             }
         }
     }
 }

2、导入Excel修改完再保存（举例为.xls格式）：

            // 载入模板文件-xls
            string excelTemplate_BaseMaterialTestReport = Path.Combine("目录", "文件名.xls");
            if (excelTemplate_BaseMaterialTestReport.Equals(".xls"))
            {
                stringBuilder.Append("Excel文件格式不为‘.xls’");
                return false;
            }

            HSSFWorkbook hssfworkbook;
            using (FileStream file = new(excelTemplate_BaseMaterialTestReport, FileMode.Open, FileAccess.Read))
            {
                hssfworkbook = new HSSFWorkbook(file);
            }
            NPOI.SS.UserModel.ISheet sheet = hssfworkbook.GetSheetAt(0);  // 找到sheet1

            // 写入数据
            DateTime dateTime = DateTime.Now;
            string dateTime_Date = dateTime.ToString();  // 日期
            sheet.GetRow(3).GetCell(8).SetCellValue(dateTime_Date);  // 日期
            sheet.GetRow(5).GetCell(6).SetCellValue("备注");  // 备注

            string targetFileName = "文件保存目标地址";  // 文件名
            // 保存Excel到指定文件夹中（xls）
            using (System.IO.MemoryStream ms = new())
            {
                hssfworkbook.Write(ms);
                using (FileStream fs = new(targetFileName, FileMode.Create, FileAccess.Write))
                {
                    byte[] data = ms.ToArray();
                    fs.Write(data, 0, data.Length);
                    fs.Flush();
                }
                hssfworkbook = null;
            }