C# 使用 NPOI操作excle文件（读取与新建重写）

1.安装NPOI:

VS直接获取NPOI nuget包，安装即可

2.操作如下:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

using System.IO;
using NPOI;
using NPOI.SS.UserModel;
using NPOI.HSSF.UserModel;
using MongoDB.Driver;
using MongoDB.Bson;

namespace KeyWordStatistic
{
    class opExcle
    {
        string _ConnectString = "mongodb://192.168.***.**:27017";
    
        
        public opExcle()
        {
            var Client = new MongoClient(_ConnectString);
            var Filter = Builders<BsonDocument>.Filter;
            var dbName = "db";
            var colName = "Parser";
            var DataBase = Client.GetDatabase(dbName);
            var DataCollection = DataBase.GetCollection<BsonDocument>(colName);
            string importExcelPath = "G:\\import.xls";
            string exportExcelPath = "G:\\export.xls";//url重复数据
            IWorkbook readWorkbook = WorkbookFactory.Create(importExcelPath);
            ISheet sheet = readWorkbook.GetSheetAt(0);//获取第一个工作薄
            IRow Columns = (IRow)sheet.GetRow(0);//获取第一行,列名

            //if (exportExcelPath.IndexOf(".xlsx") > 0) // 2007版本
            //{
            //    writeWorkbook = new XSSFWorkbook();
            //}else if (filepath.IndexOf(".xls") > 0) // 2003版本
            //    workbook = new HSSFWorkbook();
            var writeWorkbook = new HSSFWorkbook();
            var repeatSheet = writeWorkbook.CreateSheet("repeat");
            var noRepeatsheet = writeWorkbook.CreateSheet("noRepeat");
            IRow repeatSheetColumns = repeatSheet.CreateRow(0);
            IRow noRepeatSheetColumns = noRepeatsheet.CreateRow(0);
            int j = 0;
            foreach(var cell in Columns)
            {
                repeatSheetColumns.CreateCell(j).SetCellValue(cell.ToString());
                noRepeatSheetColumns.CreateCell(j).SetCellValue(cell.ToString());
                j++;
            }
            int norepeatIndex = 1;
            int repeatIndex = 1;
            //导出excel
            FileStream fs = new FileStream(exportExcelPath, FileMode.OpenOrCreate, FileAccess.ReadWrite);
            for (int i = 1; i <= sheet.LastRowNum; i++)
            {
                IRow dataItem = (IRow)sheet.GetRow(i);//获取数据
                var flag = false;
                Console.CursorLeft=0;
                Console.Write("读取第 "+i.ToString()+" 数据");
                var Curosr = DataCollection.Find(Filter.Eq("Url", dataItem.Cells[4].ToString())).ToCursor();
                int icount = 0;
                while (Curosr.MoveNext())
                {
                    icount = Curosr.Current.Count();
                }
                if (icount == 0)
                    flag= false;
                else
                    flag= true;
                int k = 0;
                if (flag)
                {
                    IRow repeatSheetRow = repeatSheet.CreateRow(repeatIndex);
                    repeatIndex++;
                    foreach (var cell in dataItem.Cells)
                    {
                        repeatSheetRow.CreateCell(k).SetCellValue(cell.ToString());
                        k++;
                    }
                }
                else
                {
                
                    IRow noRepeatSheetRow = noRepeatsheet.CreateRow(norepeatIndex);
                    norepeatIndex++;
                    foreach (var cell in dataItem.Cells)
                    {
                        noRepeatSheetRow.CreateCell(k).SetCellValue(cell.ToString());
                        k++;
                    }
                }

            }
            writeWorkbook.Write(fs);
            fs.Close();
        }

        private bool isRepeat(string url)
        {
            var Client = new MongoClient(_ConnectString);
            var Filter = Builders<BsonDocument>.Filter;
            var dbName = "db";
            var colName = "Parser";
            var DataBase = Client.GetDatabase(dbName);
            var DataCollection = DataBase.GetCollection<BsonDocument>(colName);
            var Curosr = DataCollection.Find(Filter.Eq("Url", url)).ToCursor();
            int icount = 0;
            while (Curosr.MoveNext())
            {
                icount = Curosr.Current.Count();
            }
            if (icount == 0)
                return false;
            else
                return true;
        }
    }
}