#安装NPOI

1. vs-工具-NuGet程序包管理器-管理解决方案的NuGet程序包
2. 搜索NPOI下载并安装

注：若编译器报错可选择较低版本

#选择文件

        private string SelectFolder1(TextBox tb)
        {
            string ret = "";
            System.Windows.Forms.OpenFileDialog dialog = new System.Windows.Forms.OpenFileDialog();
            if (dialog.ShowDialog() == System.Windows.Forms.DialogResult.OK)
            {
                tb.Text = dialog.FileName;
            }
            return ret;
        }

#选择文件夹

        private string SelectFolder2(TextBox tb)
        {
            string ret = "";
            System.Windows.Forms.FolderBrowserDialog dialog = new System.Windows.Forms.FolderBrowserDialog();
            if (dialog.ShowDialog() == System.Windows.Forms.DialogResult.OK)
            {
                tb.Text = dialog.SelectedPath;
            }
            return ret;
        }

#读取Excel

private void transform_Click(object sender, EventArgs e)
{
    using (FileStream fs = new FileStream(excel_folder.Text, FileMode.Open, FileAccess.Read))
    {
            XSSFWorkbook workBook = new XSSFWorkbook(fs);
            ISheet sheet = workBook.GetSheetAt(0);//读取Excel的第一个sheet
            eventName = sheet.GetRow(r).GetCell(4).ToString().Replace(" ", "");//读取Excel r行4列数据，并除去空格
    }
}

#读取txt

FileStream fs = new FileStream(@"1.TXT", FileMode.CreateOrOpen, FileAccess.Read);
StreamReader sr = new StreamReader(fs, Encoding.GetEncoding("UTF-8"));
sr.ReadLine();
sr.close();
fs.close();

#写入txt

FileStream fs = new FileStream(@"1.TXT", FileMode.Create, FileAccess.Write);
StreamWriter sw = new StreamWriter(fs, Encoding.GetEncoding("UTF-8"));
sw.WriteLine("1");
sw.close();
fs.close();