NPOI 操作Excel

2022-10-22 08:00:20

关于NPOI

NPOI是POI项目的.NET版本，是由@Tony Qu(http://tonyqus.cnblogs.com/)等大侠基于POI开发的，可以从http://npoi.codeplex.com/下载到它的最新版本。它不使用Office COM组件(Microsoft.Office.Interop.XXX.dll)，不需要安装Microsoft Office，支持对Office 97-2003的文件格式，功能比较强大。更详细的说明请看作者的博客或官方网站。

它的以下一些特性让我相当喜欢：

  1. 支持对标准的Excel读写
  2. 支持对流(Stream)的读写 (而Jet OLEDB和Office COM都只能针对文件)
  3. 支持大部分Office COM组件的常用功能
  4. 性能优异 (相对于前面的方法)
  5. 使用简单，易上手

使用NPOI

本文使用的是它当前的最新版本1.2.4，此版本的程序集缩减至2个：NPOI.dll、Ionic.Zip.dll，直接引用到项目中即可。

对于我们开发者使用的对象主要位于NPOI.HSSF.UserModel空间下，主要有HSSFWorkbook、HSSFSheet、HSSFRow、HSSFCell，对应的接口为位于NPOI.SS.UserModel空间下的IWorkbook、ISheet、IRow、ICell，分别对应Excel文件、工作表、行、列。

简单演示一下创建一个Workbook对象，添加一个工作表，在工作表中添加一行一列：

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using NPOI.HSSF.UserModel;
using NPOI.SS.UserModel;
 
public class NPOIWrite
{
    void CreateSheet()
    {
        IWorkbook workbook = new HSSFWorkbook();//创建Workbook对象
        ISheet sheet = workbook.CreateSheet("Sheet1");//创建工作表
        IRow row = sheet.CreateRow(0);//在工作表中添加一行
        ICell cell = row.CreateCell(0);//在行中添加一列
        cell.SetCellValue("test");//设置列的内容
    }
}

相应的读取代码：

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using System.IO;
using NPOI.HSSF.UserModel;
using NPOI.SS.UserModel;
 
public class NPOIRead
{
    void GetSheet(Stream stream)
    {
        IWorkbook workbook = new HSSFWorkbook(stream);//从流内容创建Workbook对象
        ISheet sheet = workbook.GetSheetAt(0);//获取第一个工作表
        IRow row = sheet.GetRow(0);//获取工作表第一行
        ICell cell = row.GetCell(0);//获取行的第一列
        string value = cell.ToString();//获取列的值
    }
}

使用NPOI导出

从DataTable读取内容来创建Workbook对象：

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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);
 
                // handling header.
                foreach (DataColumn column in table.Columns)
                    headerRow.CreateCell(column.Ordinal).SetCellValue(column.Caption);//If Caption not set, returns the ColumnName value
 
                // handling value.
                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++;
                }
 
                workbook.Write(ms);
                ms.Flush();
                ms.Position = 0;
            }
        }
    }
    return ms;
}

如果看不惯DataTable，那么DataReader也行：

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public static MemoryStream RenderToExcel(IDataReader reader)
{
    MemoryStream ms = new MemoryStream();
 
    using (reader)
    {
        using (IWorkbook workbook = new HSSFWorkbook())
        {
            using (ISheet sheet = workbook.CreateSheet())
            {
                IRow headerRow = sheet.CreateRow(0);
                int cellCount = reader.FieldCount;
 
                // handling header.
                for (int i = 0; i < cellCount; i++)
                {
                    headerRow.CreateCell(i).SetCellValue(reader.GetName(i));
                }
 
                // handling value.
                int rowIndex = 1;
                while (reader.Read())
                {
                    IRow dataRow = sheet.CreateRow(rowIndex);
 
                    for (int i = 0; i < cellCount; i++)
                    {
                        dataRow.CreateCell(i).SetCellValue(reader[i].ToString());
                    }
 
                    rowIndex++;
                }
 
                workbook.Write(ms);
                ms.Flush();
                ms.Position = 0;
            }
        }
    }
    return ms;
}

以上代码把创建的Workbook对象保存到流中，可以通过以下方法输出到浏览器，或是保存到硬盘中：

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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;
    }
}
 
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());
}

使用NPOI导入

需要注意的是，sheet.LastRowNum = sheet.PhysicalNumberOfRows - 1，这里可能存在BUG：当没有数据或只有一行数据时sheet.LastRowNum为0，PhysicalNumberOfRows 表现正常。

这里读取流中的Excel来创建Workbook对象，并转换成DataTable：

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static DataTable RenderFromExcel(Stream excelFileStream)
{
    using (excelFileStream)
    {
        using (IWorkbook workbook = new HSSFWorkbook(excelFileStream))
        {
            using (ISheet sheet = workbook.GetSheetAt(0))//取第一个表
            {
                DataTable table = new DataTable();
 
                IRow headerRow = sheet.GetRow(0);//第一行为标题行
                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;
 
            }
        }
    }
}

或者是直接生成SQL语句来插入到数据库：

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public static int RenderToDb(Stream excelFileStream, string insertSql, DBAction dbAction)
{
    int rowAffected = 0;
    using (excelFileStream)
    {
        using (IWorkbook workbook = new HSSFWorkbook(excelFileStream))
        {
            using (ISheet sheet = workbook.GetSheetAt(0))//取第一个工作表
            {
                StringBuilder builder = new StringBuilder();
 
                IRow headerRow = sheet.GetRow(0);//第一行为标题行
                int cellCount = headerRow.LastCellNum;//LastCellNum = PhysicalNumberOfCells
                int rowCount = sheet.LastRowNum;//LastRowNum = PhysicalNumberOfRows - 1
 
                for (int i = (sheet.FirstRowNum + 1); i <= rowCount; i++)
                {
                    IRow row = sheet.GetRow(i);
                    if (row != null)
                    {
                        builder.Append(insertSql);
                        builder.Append(" values (");
                        for (int j = row.FirstCellNum; j < cellCount; j++)
                        {
                            builder.AppendFormat("'{0}',", GetCellValue(row.GetCell(j)).Replace("'", "''"));
                        }
                        builder.Length = builder.Length - 1;
                        builder.Append(");");
                    }
 
                    if ((i % 50 == 0 || i == rowCount) && builder.Length > 0)
                    {
                        //每50条记录一次批量插入到数据库
                        rowAffected += dbAction(builder.ToString());
                        builder.Length = 0;
                    }
                }
            }
        }
    }
    return rowAffected;
}

这里的Excel可能没有数据，所以可以加一个方法来检测：

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public static bool HasData(Stream excelFileStream)
{
    using (excelFileStream)
    {
        using (IWorkbook workbook = new HSSFWorkbook(excelFileStream))
        {
            if (workbook.NumberOfSheets > 0)
            {
                using (ISheet sheet = workbook.GetSheetAt(0))
                {
                    return sheet.PhysicalNumberOfRows > 0;
                }
            }
        }
    }
    return false;
}
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