将datatable 导出成 .csv文件

将datatable 导出成 .csv文件
SqlConnection  conn=new  SqlConnection(System.Configuration.ConfigurationSettings.AppSettings["conn"]); 
        SqlDataAdapter  da=new  SqlDataAdapter("select  *  from  tb1",conn); 
        DataSet  ds=new  DataSet(); 
        da.Fill(ds,"table1"); 
        DataTable  dt=ds.Tables["table1"]; 
        StringWriter  sw=new  StringWriter(); 
        sw.WriteLine("自动编号,姓名,年龄"); 
        foreach(DataRow  dr  in  dt.Rows) 
        { 
          sw.WriteLine(dr["ID"]+","+dr["vName"]+","+dr["iAge"]); 
        } 
        sw.Close(); 
        Response.AddHeader("Content-Disposition",  "attachment;  filename=test.csv"); 
        Response.ContentType  =  "application/ms-excel"; 
        Response.ContentEncoding=System.Text.Encoding.GetEncoding("GB2312"); 
        Response.Write(sw); 
        Response.End();