private void DirectPrint_Click(object sender, EventArgs e)
{
isprint = false;
GenerateExcel_Click(sender, e); //使用NPOI生成excel
if (newsavefilepath != "" && isprint==true)
{
isprint = false; 
ChangeExcel2Image(newsavefilepath); //利用Spire将excel转换成图片
if (printDialog1.ShowDialog() == DialogResult.OK)
{ 
printDocument1.Print(); //打印
}
} 

}

private void Generate_Click(object sender, EventArgs e)
{
CreateExcel(); //使用NPOI生成excel内容
SaveFileDialog savedialog = new SaveFileDialog(); //弹出让用户选择excel保存路径的窗口
savedialog.Filter = " excel files(*.xlsx)|*.xlsx|All files(*.*)|*.*";
savedialog.RestoreDirectory = true;
savedialog.FileName = string.Format("销售订单审批单{0}", DateTime.Now.ToString("yyyyMMddHHmm"));
if (savedialog.ShowDialog() == DialogResult.OK)
{
//newsavefilepath是excel的保存路径
newsavefilepath = savedialog.FileName.ToString().Trim();
using (FileStream newfs = new FileStream(newsavefilepath, FileMode.Create, FileAccess.ReadWrite))
{
singlexssfwk.Write(newfs); //将生成的excel写入用户选择保存的文件路径中
newfs.Close();
}
} 
}

using NPOI.XSSF.UserModel;

XSSFWorkbook singlexssfwk;

//注意，不同的NPOI版本调用的方法不一致，这里使用的版本是2.1.3.1
private void CreatExcel() 
{ 
//获取模板excel的路径
string str = System.Environment.CurrentDirectory + "\\XXXX.xlsx";
if (File.Exists(str))
{
using (FileStream fs = new FileStream(str, FileMode.Open, FileAccess.Read))
{
singlexssfwk = new XSSFWorkbook(fs);
fs.Close();
}
//获取表
XSSFSheet xssfsheet = (XSSFSheet)singlexssfwk.GetSheetAt(0);
//创建行 
XSSFRow xssfrow1 = (XSSFRow)xssfsheet.GetRow(1);
//设置单元格内容
xssfrow1.GetCell(0).SetCellValue("...");
... ...
　　　 }
else{
... ...
}
}

using Spire.Xls; 
public void ChangeExcel2Image(string filename)
{
Workbook workbook = new Workbook();
workbook.LoadFromFile(filename);
Worksheet sheet = workbook.Worksheets[0];
sheet.SaveToImage(imagepath); //图片后缀.bmp ,imagepath自己设置
}

//在PrintPage方法中写截取图片 的代码
private void printDocument1_PrintPage(object sender, System.Drawing.Printing.PrintPageEventArgs e)
{ 
#region 如果不需要截取图片，可以不用写以下代码
GC.Collect();
Graphics g = e.Graphics; 
//imagepath是指 excel转成的图片的路径
using (Bitmap bitmap = new dBitmap(imagepath))
{
//如何截取自己摸索
Rectangle newarea = new Rectangle();
newarea.X = 0;
newarea.Y = 50;
newarea.Width = bitmap.Width;
newarea.Height = bitmap.Height - 120;
using (Bitmap newbitmap = bitmap.Clone(newarea, bitmap.PixelFormat))
{
g.DrawImage(newbitmap, 0, 0, newbitmap.Width - 200, newbitmap.Height - 150);
}
} 
#endregion
}