最近在项目中需要导出Excel。在这里做个记录。在网上查阅了一些资料。将自己最终的代码分享在这里，以供自己日后查阅，如果能给陌生的你带来方便，那便更好。
开发的过程中也遇到了一个问题，设置字体会导致打开Excel时报错（错误：此文件中的某些文本格式可能已经更改，因为它已经超出最多允许的字体数），并且设置失败。这个问题产生的原因是因为频繁的创建字体，这个在我参考的代码中是有问题，我做了些改善。如果你有更优的方案，期待向你学习。
public class ExcelDAL
{
#region 定义单元格常用到样式的枚举
public enum stylexls
{
头,
列标题,
url,
时间,
数字,
钱,
百分比,
中文大写,
科学计数法,
默认
}
#endregion
//定义工作薄
private static IWorkbook m_workbook;
//定义sheet表
private static ISheet m_sheet;
//表名
private static List<string> m_sheets=new List<string>();
private static ICellStyle m_cellStyle;
private static IDataFormat m_datastyle;
//字体
private static IFont m_font20;
//字体
private static IFont m_font12;
//字体
private static IFont m_font;
/// <summary>
/// 创建Excel表
/// </summary>
/// <param name="dt">传递datatable数据类型</param>
/// <param name="filePath">文件保存路径</param>
/// <param name="sheetName">工作表名</param>
/// <param name="headerName">表格标题名</param>
/// <returns></returns>
public static bool ExportExcel(System.Data.DataTable dt, string filePath, string sheetName,string headerName="考勤表")
{
ICellStyle cellstytle = null;
try
{
//如果Excel存在就获取IWorkbook对象，否则就重新创建
if (File.Exists(filePath))
{
FileStream fs = new FileStream(filePath, FileMode.Open, FileAccess.Read);
if (filePath.IndexOf(".xlsx") > 0) // 2007版本
m_workbook = new XSSFWorkbook(fs);
else if (filePath.IndexOf(".xls") > 0) // 2003版本
m_workbook = new HSSFWorkbook(fs);
}
else
{
//创建一个工作簿
m_workbook = new HSSFWorkbook();
}
if (m_workbook != null)
{
//获取所有SheetName
int count = m_workbook.NumberOfSheets;
//如果该工作簿不存在表就创建新表
if (count < 1)
{
//创建一个 sheet 表
m_sheet = m_workbook.CreateSheet(sheetName);
}
else
{
m_sheets.Clear();
for (int i = 0; i < count; i++)
{
m_sheet = m_workbook.GetSheetAt(i);
m_sheets.Add(m_sheet.SheetName);
}
if(m_sheets.Contains(sheetName))
{
m_sheet = m_workbook.CreateSheet(sheetName+System.DateTime.Now.ToString("HH-mm-ss")+"副本");
}
else
{
m_sheet = m_workbook.CreateSheet(sheetName);
}
}
}
else
{
return false;
}
#region 打印设置
m_sheet.PrintSetup.Copies = 3;
m_sheet.PrintSetup.Landscape = false;
m_sheet.PrintSetup.Scale = 100;
//纸张设置，A4纸
m_sheet.PrintSetup.PaperSize = 9;
//打印网格线
m_sheet.IsPrintGridlines = true;
#endregion
#region 设置表头
m_sheet.AddMergedRegion(new NPOI.SS.Util.CellRangeAddress(0, 0, 0, dt.Columns.Count-1)); //合并单元格
IRow row0 = m_sheet.CreateRow(0); //创建一行
row0.Height = 50 * 20;
ICell icelltop0 = row0.CreateCell(0); //创建一个单元格
IFont font = m_workbook.CreateFont();
font.FontHeightInPoints = 30;
icelltop0.CellStyle = Getcellstyle(m_workbook, stylexls.头);
icelltop0.SetCellValue(headerName);
#endregion
#region 设置列
IRow rowH = m_sheet.CreateRow(1);
cellstytle= Getcellstyle(m_workbook, stylexls.列标题);
//设置列名
foreach (DataColumn col in dt.Columns)
{
//创建单元格并设置单元格内容
rowH.CreateCell(col.Ordinal).SetCellValue(col.Caption);
//设置单元格格式
rowH.Cells[col.Ordinal].CellStyle = cellstytle;
}
#endregion
//写入数据
cellstytle = Getcellstyle(m_workbook, stylexls.默认);
for (int i = 0; i < dt.Rows.Count; i++)
{
//跳过前两行，第一行为标题，第二行为列名
IRow row = m_sheet.CreateRow(i + 2);
ICell cell = row.CreateCell(0);
for (int j = 0; j < dt.Columns.Count; j++)
{
cell = row.CreateCell(j);
cell.SetCellValue(dt.Rows[i][j].ToString());
cell.CellStyle = cellstytle;
}
}
//获取当前列的宽度，然后对比本列的长度，取最大值
for (int columnNum = 0; columnNum <= dt.Rows.Count; columnNum++)
{
int columnWidth = m_sheet.GetColumnWidth(columnNum) / 256;
for (int rowNum = 1; rowNum <= m_sheet.LastRowNum; rowNum++)
{
IRow currentRow;
//当前行未被使用过
if (m_sheet.GetRow(rowNum) == null)
{
currentRow = m_sheet.CreateRow(rowNum);
}
else
{
currentRow = m_sheet.GetRow(rowNum);
}
if (currentRow.GetCell(columnNum) != null)
{
ICell currentCell = currentRow.GetCell(columnNum);
int length = Encoding.Default.GetBytes(currentCell.ToString()).Length;
if (columnWidth < length)
{
columnWidth = length + 10;
}
}
}
m_sheet.SetColumnWidth(columnNum, columnWidth * 256);
//m_sheet.SetColumnWidth(0, 30 * 256);
//m_sheet.SetColumnWidth(1, 10 * 256);
//m_sheet.SetColumnWidth(2, 25 * 256);
//m_sheet.SetColumnWidth(3, 25 * 256);
//m_sheet.SetColumnWidth(4, 10 * 256);
//m_sheet.SetColumnWidth(5, 10 * 256);
}
//创建文件
FileStream file = new FileStream(filePath, FileMode.OpenOrCreate, FileAccess.Write);
//创建一个 IO 流
MemoryStream ms = new MemoryStream();
//写入到流
m_workbook.Write(ms);
//转换为字节数组
byte[] bytes = ms.ToArray();
file.Write(bytes, 0, bytes.Length);
file.Flush();
//释放资源
bytes = null;
ms.Close();
ms.Dispose();
file.Close();
file.Dispose();
m_workbook.Close();
m_sheet = null;
m_workbook = null;
m_cellStyle = null;
m_datastyle = null;
m_font = null;
m_font12 = null;
m_font20 = null;
return true;
}
catch (Exception ex)
{
return false;
}
}
#region 定义单元格常用到样式
static ICellStyle Getcellstyle(IWorkbook wb, stylexls str)
{
try
{
//CreateFont()不能频繁创建，会导致打开EXCEL表的时候报如下错误：
//此文件中的某些文本格式可能已经更改，因为它已经超出最多允许的字体数。
if (m_font20 == null)
{
m_font20 = wb.CreateFont();
m_font20.FontHeightInPoints = 20;
m_font20.FontName = "微软雅黑";
m_font20.Boldweight = (short)FontBoldWeight.Bold;
}
if (m_font12 == null)
{
m_font12 = wb.CreateFont();
m_font12.FontHeightInPoints = 12;
m_font12.FontName = "微软雅黑";
m_font12.Boldweight = (short)FontBoldWeight.Bold;
}
if (m_font == null)
{
m_font = wb.CreateFont();
m_font.FontName = "微软雅黑";
}
//if (m_cellStyle == null)
//{
m_cellStyle = wb.CreateCellStyle();
//边框
m_cellStyle.BorderBottom = NPOI.SS.UserModel.BorderStyle.Medium;
m_cellStyle.BorderLeft = NPOI.SS.UserModel.BorderStyle.Medium;
m_cellStyle.BorderRight = NPOI.SS.UserModel.BorderStyle.Medium;
m_cellStyle.BorderTop = NPOI.SS.UserModel.BorderStyle.Medium;
//边框颜色
m_cellStyle.BottomBorderColor = HSSFColor.OliveGreen.Blue.Index;
m_cellStyle.TopBorderColor = HSSFColor.OliveGreen.Blue.Index;
//背景图形
//cellStyle.FillBackgroundColor = HSSFColor.OLIVE_GREEN.BLUE.index;
//cellStyle.FillForegroundColor = HSSFColor.OLIVE_GREEN.BLUE.index;
m_cellStyle.FillForegroundColor = HSSFColor.White.Index;
// cellStyle.FillPattern = FillPatternType.NO_FILL;
m_cellStyle.FillBackgroundColor = HSSFColor.Blue.Index;
//水平对齐
m_cellStyle.Alignment = NPOI.SS.UserModel.HorizontalAlignment.Center;
//垂直对齐
m_cellStyle.VerticalAlignment = VerticalAlignment.Center;
//自动换行
m_cellStyle.WrapText = false;
//缩进
//cellStyle.Indention = 0;
//}
//创建格式
if (m_datastyle == null)
{
m_datastyle = wb.CreateDataFormat();
}
//上面基本都是设共公的设置
//下面列出了常用的字段类型
switch (str)
{
case stylexls.头:
//cellStyle.FillPattern = FillPatternType.LEAST_DOTS;
//设置为文本格式，也可以为 text，即 dataFormat.GetFormat("text");
m_cellStyle.DataFormat = m_datastyle.GetFormat("@");
m_cellStyle.SetFont(m_font20);
break;
case stylexls.列标题:
// cellStyle.FillPattern = FillPatternType.LEAST_DOTS;
m_cellStyle.DataFormat = m_datastyle.GetFormat("@");
m_cellStyle.SetFont(m_font12);
break;
case stylexls.时间:
m_cellStyle.DataFormat = m_datastyle.GetFormat("yyyy/mm/dd");
m_cellStyle.SetFont(m_font);
break;
case stylexls.数字:
m_cellStyle.DataFormat = HSSFDataFormat.GetBuiltinFormat("0.00");
m_cellStyle.SetFont(m_font);
break;
case stylexls.钱:
m_cellStyle.DataFormat = m_datastyle.GetFormat("￥#,##0");
m_cellStyle.SetFont(m_font);
break;
case stylexls.url:
//IFont fontcolorblue = wb.CreateFont();
//fontcolorblue.Color = HSSFColor.OliveGreen.Blue.Index;
//fontcolorblue.IsItalic = true;//下划线
////fontcolorblue.Underline = 1;
//fontcolorblue.FontName = "微软雅黑";
//m_cellStyle.SetFont(fontcolorblue);
break;
case stylexls.百分比:
m_cellStyle.DataFormat = HSSFDataFormat.GetBuiltinFormat("0.00%");
m_cellStyle.SetFont(m_font);
break;
case stylexls.中文大写:
m_cellStyle.DataFormat = m_datastyle.GetFormat("[DbNum2][$-804]0");
m_cellStyle.SetFont(m_font);
break;
case stylexls.科学计数法:
m_cellStyle.DataFormat = HSSFDataFormat.GetBuiltinFormat("0.00E+00");
m_cellStyle.SetFont(m_font);
break;
case stylexls.默认:
m_cellStyle.SetFont(m_font);
break;
}
return m_cellStyle;
}
catch
{
return m_cellStyle;
}
}
#endregion
}创建的表格的效果如图所示：
