DataTable Excel 导出：

    public static class CSVFileHelper
    {

        public static string ToHtmlTable(this DataTable target)
        {
            return DataTableToHtmlTable(target);
        }

        public static string ToRootExcelFile(this DataTable target,string _fileName)
        {
            return SaveDataTableToRootExcelFile(_fileName, target);
        }


        public static string DataTableToHtmlTable(DataTable sourceData)
        {
            //
            var sbHtml = new StringBuilder();
            sbHtml.Append("<table border='1' cellspacing='0' cellpadding='0'>");

            sbHtml.Append("<tr>");
            DataColumnCollection columns = sourceData.Columns;
            foreach (DataColumn col in columns)
            {
                sbHtml.AppendFormat("<td style='font-size: 14px;text-align:center;background-color: #DCE0E2; font-weight:bold;' height='25'>{0}</td>", col.ColumnName);
            }
            sbHtml.Append("</tr>");

            foreach (DataRow row in sourceData.Rows)
            {
                sbHtml.Append("<tr>");
                foreach (DataColumn col in columns)
                {
                    sbHtml.AppendFormat("<td style='font-size: 12px;height:20px;'>{0}</td>", row[col]);
                }
                sbHtml.Append("</tr>");
            }
            sbHtml.Append("</table>");
            return sbHtml.ToString();
        }

        /// <summary>
        /// 
        /// </summary>
        /// <param name="_fileName"></param>
        /// <param name="sourceData"></param>
        /// <returns></returns>
        public static string SaveDataTableToRootExcelFile(string _fileName,DataTable sourceData)
        {
            string FileName = _fileName;
            string dir = HttpRuntime.AppDomainAppPath.ToString() + "/SaveExcelFile/";

            FileName = dir + FileName;

            if (!Directory.Exists(dir))
            {
                Directory.CreateDirectory(dir);
            }

            int numWriter = 1000;
            int numRecord = sourceData.Rows.Count;

            var sbHtml = new StringBuilder();
            sbHtml.Append("<table border='1' cellspacing='0' cellpadding='0'>");

            sbHtml.Append("<tr>");
            DataColumnCollection columns = sourceData.Columns;
            foreach (DataColumn col in columns)
            {
                sbHtml.AppendFormat("<td style='font-size: 14px;text-align:center;background-color: #DCE0E2; font-weight:bold;' height='25'>{0}</td>", col.ColumnName);
            }
            sbHtml.Append("</tr>");


            using (FileStream fs = File.Open(FileName, FileMode.CreateNew, FileAccess.Write))
            {
                using (StreamWriter sw = new StreamWriter(fs))
                {
                    try
                    {
                        sw.Write(sbHtml.ToString());

                        sbHtml.Clear();

                        int i = 0;
                        foreach (DataRow row in sourceData.Rows)
                        {

                            sbHtml.Append("<tr>");
                            foreach (DataColumn col in columns)
                            {
                                sbHtml.AppendFormat("<td style='font-size: 12px;height:20px;'>{0}</td>", row[col]);
                            }
                            sbHtml.Append("</tr>");
                            i++;

                            if (i == 1000)
                            {
                                i = 0;
                                sw.Write(sbHtml.ToString());
                                sbHtml.Clear();
                            }
                        }
                        sw.Write("</table>");
                        sw.Close();
                        fs.Close();
                    }
                    catch (Exception ex)
                    {
                        sw.Close();
                        fs.Close();
                    }
                }
            }

            return FileName;
        }

        /// <summary>
        /// 将DataTable中数据写入到CSV文件中
        /// </summary>
        /// <param name="dt">提供保存数据的DataTable</param>
        /// <param name="fullPath">CSV的文件路径</param>
        public static void SaveCSV(DataTable dt, string fullPath)
        {
            FileInfo fi = new FileInfo(fullPath);
            if (!fi.Directory.Exists)
            {
                fi.Directory.Create();
            }
            FileStream fs = new FileStream(fullPath, System.IO.FileMode.Create, System.IO.FileAccess.Write);
            StreamWriter sw = new StreamWriter(fs, System.Text.Encoding.UTF8);
            string data = "";
            //写出列名称
            for (int i = 0; i < dt.Columns.Count; i++)
            {
                data += dt.Columns[i].ColumnName.ToString();
                if (i < dt.Columns.Count - 1)
                {
                    data += ",";
                }
            }
            sw.WriteLine(data);
            //写出各行数据
            for (int i = 0; i < dt.Rows.Count; i++)
            {
                data = "";
                for (int j = 0; j < dt.Columns.Count; j++)
                {
                    string str = dt.Rows[i][j].ToString();
                    str = str.Replace("\"", "\"\"");//替换英文冒号 英文冒号需要换成两个冒号
                    if (str.Contains(',') || str.Contains('"')
                        || str.Contains('\r') || str.Contains('\n')) //含逗号 冒号 换行符的需要放到引号中
                    {
                        str = string.Format("\"{0}\"", str);
                    }

                    data += str;
                    if (j < dt.Columns.Count - 1)
                    {
                        data += ",";
                    }
                }
                sw.WriteLine(data);
            }
            sw.Close();
            fs.Close();
        }

        /// <summary>
        /// 将CSV文件的数据读取到DataTable中
        /// </summary>
        /// <param name="filePath">CSV文件路径</param>
        /// <returns>返回读取了CSV数据的DataTable</returns>
        public static DataTable OpenCSV(string filePath)
        {
            Encoding encoding = Encoding.GetEncoding("GB2312");
            DataTable dt = new DataTable();
            FileStream fs = new FileStream(filePath, System.IO.FileMode.Open, System.IO.FileAccess.Read);

            StreamReader sr = new StreamReader(fs, encoding);
            //记录每次读取的一行记录
            string strLine = "";
            //记录每行记录中的各字段内容
            string[] aryLine = null;
            string[] tableHead = null;
            //标示列数
            int columnCount = 0;
            //标示是否是读取的第一行
            bool IsFirst = true;
            //逐行读取CSV中的数据
            while ((strLine = sr.ReadLine()) != null)
            {

                if (IsFirst == true)
                {
                    tableHead = strLine.Split(',');
                    IsFirst = false;
                    columnCount = tableHead.Length;
                    //创建列
                    for (int i = 0; i < columnCount; i++)
                    {
                        DataColumn dc = new DataColumn(tableHead[i]);
                        dt.Columns.Add(dc);
                    }
                }
                else
                {
                    aryLine = strLine.Split(',');
                    DataRow dr = dt.NewRow();
                    for (int j = 0; j < columnCount; j++)
                    {
                        dr[j] = aryLine[j];
                    }
                    dt.Rows.Add(dr);
                }
            }
            if (aryLine != null && aryLine.Length > 0)
            {
                dt.DefaultView.Sort = tableHead[0] + " " + "asc";
            }

            sr.Close();
            fs.Close();
            return dt;
        }
    }