.NET中Excel与DataTable之间的互相转换

花费一下午，从各大博主的代码当中总算是把这个功能给实现了，主要的目的是让大家明白原理。如果出现大佬代码被我爬进来了，需要删除的滴滴我哦。还有就是主要所有的代码看不懂的记得看注释，比较更多的都是写在代码的注释里的。

先把前端的跟点击事件贴一下吧

 划重点，前端有哪些东西呢？

1. 上传控件！Ibmsg
2. 两个按钮！btn1，btn2
3. 数据表！GridView1

然后是第一段代码段

        /// 

        /// 点击读取按钮执行
        /// 
        /// 
        /// 
        protected void Button1_Click(object sender, EventArgs e)
        {
            //数据表不解释
            DataTable dt;
            //执行方法读取数据表。
            dt = ExcelToDataTable();
            //读取后防止回发先存着待会转excel的时候用！
            ViewState["dt"] = dt;
            //控件填充
            GridView1.DataSource = dt;
            GridView1.DataBind();
        }

        


        /// 

        /// 读取excel转化成datatable
        /// 
        /// 
        /// 
        public DataTable ExcelToDataTable()
        {
            //别问我这个干嘛的，一下想不起来了
            string sheetName;
            //获取上传控件
            FileUpload fileUpload = fuload;
            //HasFile看看控件是不是选好文件了，没有就抬走
            if (!fileUpload.HasFile)
            {
                return null;
            }
            //把你上传的表放进服务里面去，待会用
            string path = HttpContext.Current.Server.MapPath(@"~/temp/");
            if (!Directory.Exists(path))
            {
                Directory.CreateDirectory(path);
            }
            string newFileName = Guid.NewGuid().ToString("N") + Path.GetExtension(fileUpload.FileName);
            fileUpload.SaveAs(path + newFileName);

            //数据库方面的就是把excel当成一个数据库，然后开始生成与创建连接字符串
            string strConn = string.Empty;
            switch (Path.GetExtension(fileUpload.FileName))
            {
                case ".xlsx":
                    strConn = "Provider=Microsoft.Ace.OleDb.12.0;Data Source=" + path + newFileName + ";Extended Properties='Excel 12.0 Xml; HDR=YES; IMEX=1'";
                    break;
                case ".xls":
                    strConn = "Provider=Microsoft.Jet.OleDb.4.0;" + "data source=" + path + newFileName + ";Extended Properties='Excel 8.0; HDR=YES; IMEX=1'";
                    break;
                default:
                    return null;
            }

            try
            {
                //创建数据源链接对象，添加连接字符串，然后打开
                OleDbConnection conn1 = new OleDbConnection(strConn);
                conn1.Open();
                //获取表基本信息
                DataTable dtSheetName = conn1.GetOleDbSchemaTable(OleDbSchemaGuid.Tables, new object[] { null, null, null, "Table" });
                //把excel底下的附表名获取到，然后关闭
                string[] strTableNames = new string[dtSheetName.Rows.Count];
                sheetName = dtSheetName.Rows[0]["TABLE_NAME"].ToString();
                conn1.Close();
                conn1.Dispose();
                //然后开始查询表
                DataTable dtTemp = new DataTable();
                string strExcelTemp = string.Format("select top 1 * from [{0}]", sheetName);

                //后面的代码自己去理解吧，查出来以后返回datatable
                DataTable dt = new DataTable();
                string strExcel = string.Format("select * from [{0}]", sheetName);
                using (OleDbConnection conn = new OleDbConnection(strConn))
                {
                    using (OleDbDataAdapter myCommand = new OleDbDataAdapter(strExcelTemp, strConn.Replace("HDR=YES", "HDR=NO")))
                    {
                        myCommand.Fill(dtTemp);
                    }

                    if (dtTemp != null && dtTemp.Rows.Count == 1)
                    {
                        //前三列不为空
                        strExcel += " where " + dtTemp.Rows[0][0] + " is not null and " + dtTemp.Rows[0][1] + " is not null and " + dtTemp.Rows[0][0] + " is not null ";
                        using (OleDbDataAdapter myCommand = new OleDbDataAdapter(strExcel, strConn))
                        {
                            myCommand.Fill(dt);
                        }
                    }
                    else
                    {
                        using (OleDbDataAdapter myCommand = new OleDbDataAdapter(strExcel, strConn))
                        {
                            myCommand.Fill(dt);
                        }
                    }
                }

                return dt;
            }
            catch (Exception e)
            {
                return null;
            }
            finally
            {
                if (File.Exists(path + newFileName))
                {
                    File.Delete(path + newFileName);
                }
            }
        }

前面的部分就是读取Excel数据用的，读取完后将读出来的DataTable填充到了GridView里面。接下来则是将他读取出来生成Excel表重新保存到指定的路径去。

        /// 

        /// 点击生成Excel文件并且打它
        /// 
        /// 
        /// 
        protected void Button1_Click1(object sender, EventArgs e)
        {
            //重点就是这个ViewState["dt"]，别问我哪里来的，就在上一个方法中存下来的
            string dizhi =DataToExcel((DataTable)ViewState["dt"], "1");
            //后面的代码就是打开指定文件的自己看
            System.Diagnostics.ProcessStartInfo info = new System.Diagnostics.ProcessStartInfo();
            //info.WorkingDirectory = Application.StartupPath;
            info.FileName = dizhi;
            info.Arguments = "";
            try
            {
                System.Diagnostics.Process.Start(info);
            }
            catch (System.ComponentModel.Win32Exception we)
            {
                return;
            }
        }

        /// 

        /// Datatable生成Excel表格并返回路径
        /// 
        /// Datatable
        /// 文件名
        /// 
        public string DataToExcel(DataTable m_DataTable, string s_FileName)
        {
            //显示设置路径嘛,为了方便，直接放d盘下吧
            string FileName = "d:/" + s_FileName + ".xls";
            //然后是判断这个文件是不是存在，如果存在，删除，不存在，过
            if (File.Exists(FileName))                                
            {
                File.Delete(FileName);
            }
            //下面是一系列的读写代码，直接拷贝吧
            FileStream objFileStream;
            StreamWriter objStreamWriter;
            string strLine = "";
            objFileStream = new FileStream(FileName, FileMode.OpenOrCreate, FileAccess.Write);
            objStreamWriter = new StreamWriter(objFileStream, Encoding.Unicode);
            //先把第一行拿出来，这是标题
            for (int i = 0; i < m_DataTable.Columns.Count; i++)
            {
                strLine = strLine + m_DataTable.Columns[i].Caption.ToString() + Convert.ToChar(9);     
            }
            objStreamWriter.WriteLine(strLine);
            strLine = "";
            //然后再循环一次，把内容填充进去
            for (int i = 0; i < m_DataTable.Rows.Count; i++)
            {
                for (int j = 0; j < m_DataTable.Columns.Count; j++)
                {
                    if (m_DataTable.Rows[i].ItemArray[j] == null)
                        strLine = strLine + " " + Convert.ToChar(9);                                    
                    else
                    {
                        string rowstr = "";
                        rowstr = m_DataTable.Rows[i].ItemArray[j].ToString();
                        if (rowstr.IndexOf("\r\n") > 0)
                            rowstr = rowstr.Replace("\r\n", " ");
                        if (rowstr.IndexOf("\t") > 0)
                            rowstr = rowstr.Replace("\t", " ");
                        strLine = strLine + rowstr + Convert.ToChar(9);
                    }
                }
                objStreamWriter.WriteLine(strLine);
                strLine = "";
            }
            objStreamWriter.Close();
            objFileStream.Close();
            //填充完后关闭读写流，将刚刚的路径给放回就行了
            return FileName;        
        }

就这样，就结束了，自己看吧，不懂再说。