using System;
using System.Data;
using System.Data.SqlClient;

public class ADO_NET
{
    public ActionResult ExportData()
    {
        string sAbsolutePath = "xxx";
        string FileName = string.Format("AQ_{0}.csv", DateTime.Now.ToString("yyyyMMddHHmmss"));

        try
        {
            FinCapDbContext db = DbContextFactory.GetCurrentContext();
            SqlConnection conn = new SqlConnection(db.CurrentConnectionString);
            conn.Open();
            SqlCommand cmd = new SqlCommand("SQL Statement", conn);
            cmd.CommandTimeout = 1200;
            SqlDataReader sdr = cmd.ExecuteReader();
            StreamWriter sw = new StreamWriter(sAbsolutePath + "\\" + FileName, false, Encoding.GetEncoding("GB2312"));
            StringBuilder sb = new StringBuilder();
            int k = 0;
            for (int m = 0; m < sdr.FieldCount; m++)
            {
                sb.Append(sdr.GetName(m) + ",");
            }
            sb.Append(Environment.NewLine);

            while (sdr.Read())
            {
                k++;
                for (int n = 0; n < sdr.FieldCount; n++)
                {
                    sb.Append(sdr[n] + ",");
                }
                sb.Append(Environment.NewLine);

                if (k > 20000)
                {
                    k = 0;
                    sw.Write(sb.ToString());
                    sb.Length = 0;
                }
            }

            if (k <= 20000)
            {
                sw.Write(sb.ToString());
            }

            sw.Flush();
            sw.Close();
            conn.Close();
            return File(sAbsolutePath + "\\" + FileName, "application/zip-x-compressed", FileName);
        }
        catch
        {
            return File("xxx");
        }
    }
}