请教，嵌套循环的问题

Question

最近做NPOI导出EXCEL，之前给边框加粗线。        for (int i = 0; i <= 1; i++)
            {
                for(int j = 0; j <= 2; j++)
                {
                    s.GetRow(i).GetCell(j).CellStyle = style;
                }
                
            }结果报错了，引发的异常:“System.NullReferenceException”我就单独做一个，for (int i = 0; i <= 2; i++)
            {
                for (int j = 0; j <= 5; j++)
                {
                    Console.Write("{i}:{j}", i , j);
                    
                }
                Console.WriteLine();
            }结果还是报错，
“System.FormatException”类型的未经处理的异常在 mscorlib.dll 中发生 其他信息: 输入字符串的格式不正确。
不知怎么写才正确，指教一下，谢谢。

Answer 1

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;namespace ConsoleApplication1
{
    class Program
    {
        static void Main(string[] args)
        {
            try
            {
                for (int i = 0; i <= 2; i++)
                {
                    for (int j = 0; j <= 5; j++)
                    {
                        Console.Write("i是{0},j是{1}", i, j);
                        Console.Write("\n ");                    }
                    Console.WriteLine();                }
                Console.ReadLine();            }
            catch (Exception ex)
            {
                
                throw;
            }
           
        }
    }
}

Answer 2

 s.GetRow(i).GetCell(j).CellStyle = style;第一段代码，i 和 j ,这个怎么解决呢？？？

Answer 3

https://www.cnblogs.com/siyunianhua/p/6852750.html 
https://www.cnblogs.com/luowende2012/archive/2012/07/28/2612848.html

Answer 4

sheet.Cells[i , j]

Answer 5

private void button1_Click(object sender, EventArgs e)
        {
            Form1 f = new Form1();            ISheet s = w.CreateSheet("a");
            w.CreateSheet("b");
            w.CreateSheet("c");            IRow r= s.CreateRow(1);            ICell cell= r.CreateCell(1);
            
            ICellStyle style = w.CreateCellStyle();
            style.BorderBottom = NPOI.SS.UserModel.BorderStyle.Thick;
            style.BorderLeft = NPOI.SS.UserModel.BorderStyle.Thin;
            style.BorderRight = NPOI.SS.UserModel.BorderStyle.Thin;
            style.BorderTop = NPOI.SS.UserModel.BorderStyle.Thin;            ICellStyle cel = gets();            s.CreateRow(0).CreateCell(0).SetCellValue("测试1");
            s.GetRow(0).CreateCell(1).SetCellValue("测试2");
            s.GetRow(0).CreateCell(2).SetCellValue(textBox2.Text);            
            s.CreateRow(1).CreateCell(0).SetCellValue("测试222");
            s.CreateRow(1).CreateCell(1).SetCellValue(Convert.ToDouble(textBox1.Text));
            s.GetRow(1).CreateCell(2).SetCellValue(Convert.ToDouble(textBox2.Text));
  
            for (int i = 0; i <= 1; i++)
            {
                for(int j = 0; j <= 2; j++)
                {
                    s.GetRow(i).GetCell(j).CellStyle = style;
                }
                
            }

            s.CreateRow(2).CreateCell(1).SetCellValue(f.textBox1.Text);
            s.GetRow(2).CreateCell(2).SetCellValue(f.textBox2.Text);
            s.GetRow(2).CreateCell(3).SetCellValue(label5.Text);
   
            FileStream file = new FileStream(@"test.xls", FileMode.Create);            w.Write(file);            file.Close();
        }