FileStream FS = new FileStream(@"H:\test1.xls", FileMode.Create);   //新建xls文件

using NPOI.HSSF.UserModel;
using NPOI.SS.UserModel;
using System.IO;

 HSSFWorkbook HB = new HSSFWorkbook();
 ISheet Sheet1 = HB.CreateSheet("One");  //创建一个Sheet

Sheet1.SetColumnWidth(0, 15 * 256);
Sheet1.SetColumnWidth(1, 15 * 256);
Sheet1.SetColumnWidth(2, 15 * 256);
Sheet1.SetColumnWidth(3, 15 * 256);

for (int i = 0; i < 10; i++)
{
      IRow row1 = Sheet1.CreateRow(i);
      row1.Height = 20 * 20;      　　//设置行高
      for (int j = 0; j < 10; j++)
      {
          ICell cell1 = row1.CreateCell(j);
          cell1.SetCellValue("第" + (i + 1) + "行，第" + (j + 1) + "列");
      }
}
HB.Write(FS);　　//把流写入excel

 //CellRangeAddress（）该方法的参数次序是：开始行号，结束行号，开始列号，结束列号。
Sheet1.AddMergedRegion(new NPOI.SS.Util.CellRangeAddress(11, 13, 0, 3));

    using System;  
    using System.Collections.Generic;  
    using System.Linq;  
    using System.Text;  
    using System.Threading.Tasks;  
    using NPOI.HSSF.UserModel;  
    using NPOI.SS.Formula.Eval;  
    using NPOI.SS.Formula.Functions;  
    using NPOI.SS.UserModel;  
    using NPOI.XSSF.UserModel;  
    using NPOI.POIFS.FileSystem;  
    using NPOI.HPSF;  
    using System.IO;  
    using NPOI.SS.Util;  
    using System.Drawing;  
    using NPOI.HSSF.Util;  
      
    namespace NPOI  
    {  
        class Program3  
        {  
            static void Main(string[] args)  
            {  
                //说明：设置单元格对齐方式  
      
                //1.创建EXCEL中的Workbook           
                IWorkbook myworkbook = new XSSFWorkbook();  
      
                //2.创建Workbook中的Sheet          
                ISheet mysheet = myworkbook.CreateSheet("sheet1");  
      
                mysheet.SetColumnWidth(0, 24 * 256);  
                mysheet.SetColumnWidth(1, 24 * 256);  
                mysheet.SetColumnWidth(2, 24 * 256);  
                mysheet.SetColumnWidth(3, 24 * 256);  
      
                //3.创建Row中的Cell并赋值  
                IRow row0 = mysheet.CreateRow(0);  
                row0.Height = 50 * 20;  
                row0.CreateCell(0).SetCellValue("对齐方式");  
                row0.CreateCell(1).SetCellValue("对齐方式");  
                row0.CreateCell(2).SetCellValue("对齐方式");  
                row0.CreateCell(3).SetCellValue("对齐方式");  
      
                IRow row1 = mysheet.CreateRow(1);  
                row1.Height = 50 * 20;  
                row1.CreateCell(0).SetCellValue("对齐方式");  
                row1.CreateCell(1).SetCellValue("Shanghai is the largest city by population in ");  
                row1.CreateCell(2).SetCellValue("对齐方式");  
                row1.CreateCell(3).SetCellValue("对齐方式");  
      
                //4.创建CellStyle  
                ICellStyle style0 = myworkbook.CreateCellStyle();  
                style0.Alignment = HorizontalAlignment.General;//【General】数字、时间默认：右对齐；BOOL：默认居中；字符串：默认左对齐  
      
                ICellStyle style1 = myworkbook.CreateCellStyle();  
                style1.Alignment = HorizontalAlignment.Left;//【Left】左对齐  
      
                ICellStyle style2 = myworkbook.CreateCellStyle();  
                style2.Alignment = HorizontalAlignment.Center;//【Center】居中  
      
                ICellStyle style3 = myworkbook.CreateCellStyle();  
                style3.Alignment = HorizontalAlignment.Right;//【Right】右对齐  
      
                ICellStyle style4 = myworkbook.CreateCellStyle();  
                style4.Alignment = HorizontalAlignment.Fill;//【Fill】填充  
      
                ICellStyle style5 = myworkbook.CreateCellStyle();  
                style5.Alignment = HorizontalAlignment.Justify;//【Justify】两端对齐[会自动换行]（主要针对英文）  
      
                ICellStyle style6 = myworkbook.CreateCellStyle();  
                style6.Alignment = HorizontalAlignment.CenterSelection;//【CenterSelection】跨列居中  
      
                ICellStyle style7 = myworkbook.CreateCellStyle();  
                style7.Alignment = HorizontalAlignment.Distributed;//【Distributed】分散对齐[会自动换行]  
      
                //【Tips】  
                // 1.通过ICellStyle的VerticalAlignment属性可以设置垂直对齐模式与水平对齐无异 不再演示  
                // 2.通过ISheet的SetDefaultColumnStyle(int column, ICellStyle style)方法可以设置整列的默认单元格样式;  
                  
                //5.将CellStyle应用于具体单元格  
                row0.GetCell(0).CellStyle = style0;  
                row0.GetCell(1).CellStyle = style1;  
                row0.GetCell(2).CellStyle = style2;  
                row0.GetCell(3).CellStyle = style3;  
      
                row1.GetCell(0).CellStyle = style4;  
                row1.GetCell(1).CellStyle = style5;  
                row1.GetCell(2).CellStyle = style6;  
                row1.GetCell(3).CellStyle = style7;  
      
                //6.保存         
                FileStream file = new FileStream(@"E:\myworkbook3.xlsx", FileMode.Create);  
                myworkbook.Write(file);  
                file.Close();  
            }  
        }  
    }