我这里的txt文件里面存储的是客户的电话号码，并且是有回车换行的。

导入方法：

 ///
    /// 导入，将Txt文件转换为DataTable
    ///
    /// 文件地址
    public static DataTable Txt_DataTable(string path)
    {
        DataTable dt = new DataTable();
        dt.Columns.Add("callNumber");
        DataRow row = null;

        if (File.Exists(path) == true)
        {
            StreamReader objReader = new StreamReader(path);
            string sLine = "";
            ArrayList LineList = new ArrayList();
            while (sLine != null)
            {
                sLine = objReader.ReadLine();
                if (sLine != null && !sLine.Equals(""))
                {
                    row = dt.NewRow();
                    row["callNumber"] = sLine;
                    dt.Rows.Add(row);
                }
            }
            objReader.Close();
        }
        if (dt.Rows.Count > 0)
        {
            return dt;
        }
        else
        {
            return null;
        }
    }

导出：

方法一： 

HttpResponse resp = System.Web.HttpContext.Current.Response;
resp.ContentEncoding = System.Text.Encoding.GetEncoding("GB2312");
resp.AppendHeader("Content-Disposition", "attachment;filename=" + HttpUtility.UrlPathEncode(FileName));
resp.Write(sb.ToString());

方法二： 

Console.WriteLine(sb.ToString());
FileStream aFile = new FileStream("D:\\temp\\lintest.dat", FileMode.OpenOrCreate);
StreamWriter sw = new StreamWriter(aFile);
sw.Write(sb.ToString());
sw.Close();

方法三： 下载到客户端

Response.Clear();
Response.Buffer = true;
Response.ContentType = "text/richtext";
Response.AddHeader("content-disposition", "attachment; filename=" + HttpUtility.UrlEncode(FileName, Encoding.UTF8) + ";size=0");
Response.Write(sb.ToString());
Response.Flush();
Response.End();