NpoI

using System;
using System.Collections.Generic;
using System.Data;
using System.IO;
using System.Text;
using System.Web;
using NPOI;
using NPOI.HPSF;
using NPOI.HSSF;
using NPOI.HSSF.UserModel;
using NPOI.HSSF.Util;
using NPOI.POIFS;
using NPOI.Util;
using NPOI.SS.UserModel;
using NPOI.SS.Util;

namespace ERN.Tools.Common
{
/// <summary>
/// NPOI操作帮助类
/// </summary>
public class NPOIHelper
{
/// <summary>
/// DataTable导出到Excel文件
/// </summary>
/// <param name="dtSource">源DataTable</param>
/// <param name="strHeaderText">表头文本</param>
/// <param name="strFileName">保存位置</param>
public static void Export(DataTable dtSource, string strHeaderText, string strFileName)
{
using (MemoryStream ms = Export(dtSource, strHeaderText))
{
using (FileStream fs = new FileStream(strFileName, FileMode.Create, FileAccess.Write))
{
byte[] data = ms.ToArray();
fs.Write(data, 0, data.Length);
fs.Flush();
}
}
}

/// <summary>
/// DataTable导出到Excel的MemoryStream
/// </summary>
/// <param name="dtSource">源DataTable</param>
/// <param name="strHeaderText">表头文本</param>
public static MemoryStream Export(DataTable dtSource, string strHeaderText)
{
HSSFWorkbook workbook = new HSSFWorkbook();
ISheet sheet = workbook.CreateSheet();

ICellStyle dateStyle = workbook.CreateCellStyle();
IDataFormat format = workbook.CreateDataFormat();
dateStyle.DataFormat = format.GetFormat("yyyy-MM-dd");

#region 取得每列的列宽（最大宽度）
int[] arrColWidth = new int[dtSource.Columns.Count];
foreach (DataColumn item in dtSource.Columns)
{
//GBK对应的code page是CP936
arrColWidth[item.Ordinal] = Encoding.GetEncoding(936).GetBytes(item.ColumnName.ToString()).Length;
}
for (int i = 0; i < dtSource.Rows.Count; i++)
{
for (int j = 0; j < dtSource.Columns.Count; j++)
{
int intTemp = Encoding.GetEncoding(936).GetBytes(dtSource.Rows[i][j].ToString()).Length;
if (intTemp > arrColWidth[j])
{
arrColWidth[j] = intTemp;
}
}
}
#endregion

int rowIndex = 0;

foreach (DataRow row in dtSource.Rows)
{
#region 新建表，填充表头，填充列头，样式
if (rowIndex == 65535 || rowIndex == 0)
{
if (rowIndex != 0)
{
sheet = workbook.CreateSheet();
}

#region 表头及样式
{
IRow headerRow = sheet.CreateRow(0);
headerRow.HeightInPoints = 25;
headerRow.CreateCell(0).SetCellValue(strHeaderText);

ICellStyle headStyle = workbook.CreateCellStyle();
headStyle.Alignment = HorizontalAlignment.Center;
IFont font = workbook.CreateFont();
font.FontHeightInPoints = 20;
font.Boldweight = 700;
headStyle.SetFont(font);

headerRow.GetCell(0).CellStyle = headStyle;

sheet.AddMergedRegion(new CellRangeAddress(0, 0, 0, dtSource.Columns.Count - 1));
}
#endregion

#region 列头及样式
{
IRow headerRow = sheet.CreateRow(1);
ICellStyle headStyle = workbook.CreateCellStyle();
headStyle.Alignment = HorizontalAlignment.Center;
IFont font = workbook.CreateFont();
font.FontHeightInPoints = 10;
font.Boldweight = 700;
headStyle.SetFont(font);

foreach (DataColumn column in dtSource.Columns)
{
headerRow.CreateCell(column.Ordinal).SetCellValue(column.ColumnName);
headerRow.GetCell(column.Ordinal).CellStyle = headStyle;

//设置列宽
sheet.SetColumnWidth(column.Ordinal, (arrColWidth[column.Ordinal] + 1) * 256);

}
}
#endregion

rowIndex = 2;
}
#endregion

#region 填充内容
ICellStyle contentStyle = workbook.CreateCellStyle();
contentStyle.Alignment = HorizontalAlignment.Left;
IRow dataRow = sheet.CreateRow(rowIndex);
foreach (DataColumn column in dtSource.Columns)
{
ICell newCell = dataRow.CreateCell(column.Ordinal);
newCell.CellStyle = contentStyle;

string drValue = row[column].ToString();

switch (column.DataType.ToString())
{
case "System.String"://字符串类型
newCell.SetCellValue(drValue);
break;
case "System.DateTime"://日期类型
DateTime dateV;
DateTime.TryParse(drValue, out dateV);
newCell.SetCellValue(dateV);

newCell.CellStyle = dateStyle;//格式化显示
break;
case "System.Boolean"://布尔型
bool boolV = false;
bool.TryParse(drValue, out boolV);
newCell.SetCellValue(boolV);
break;
case "System.Int16"://整型
case "System.Int32":
case "System.Int64":
case "System.Byte":
int intV = 0;
int.TryParse(drValue, out intV);
newCell.SetCellValue(intV);
break;
case "System.Decimal"://浮点型
case "System.Double":
double doubV = 0;
double.TryParse(drValue, out doubV);
newCell.SetCellValue(doubV);
break;
case "System.DBNull"://空值处理
newCell.SetCellValue("");
break;
default:
newCell.SetCellValue("");
break;
}

}
#endregion

rowIndex++;
}

using (MemoryStream ms = new MemoryStream())
{
workbook.Write(ms);
ms.Flush();
ms.Position = 0;

//sheet.Dispose();
//workbook.Dispose();//一般只用写这一个就OK了，他会遍历并释放所有资源，但当前版本有问题所以只释放sheet
return ms;
}

}

/// <summary>
/// 用于Web导出
/// </summary>
/// <param name="dtSource">源DataTable</param>
/// <param name="strHeaderText">表头文本</param>
/// <param name="strFileName">文件名</param>
//public static void ExportByWeb(DataTable dtSource, string strHeaderText, string strFileName)
//{

// HttpContext curContext = HttpContext.Current;

// // 设置编码和附件格式
// curContext.Response.ContentType = "application/vnd.ms-excel";
// curContext.Response.ContentEncoding = Encoding.UTF8;
// curContext.Response.Charset = "";
// curContext.Response.AppendHeader("Content-Disposition",
// "attachment;filename=" + HttpUtility.UrlEncode(strFileName + ".xls", Encoding.UTF8));

// curContext.Response.BinaryWrite(Export(dtSource, strHeaderText).GetBuffer());
// curContext.Response.End();

//}

/// <summary>读取excel
/// 默认第一行为标头
/// </summary>
/// <param name="strFileName">excel文档路径</param>
/// <returns></returns>
public static DataTable Import(string strFileName)
{
DataTable dt = new DataTable();

HSSFWorkbook hssfworkbook;
using (FileStream file = new FileStream(strFileName, FileMode.Open, FileAccess.Read))
{
hssfworkbook = new HSSFWorkbook(file);
}
ISheet sheet = hssfworkbook.GetSheetAt(0);
System.Collections.IEnumerator rows = sheet.GetRowEnumerator();

IRow headerRow = sheet.GetRow(0);
int cellCount = headerRow.LastCellNum;

for (int j = 0; j < cellCount; j++)
{
ICell cell = headerRow.GetCell(j);
dt.Columns.Add(cell.ToString());
}

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

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

dt.Rows.Add(dataRow);
}
return dt;
}

}
}