Hi,

There is a sample as below. link.aspx is listing all of the files avaliable in folder and click the hyperlink in link.aspx will trigger downloading this file in downloading.aspx.

link.aspx:

using System.IO;


   protected void Page_Load(object sender, EventArgs e)
    {
        DirectoryInfo di = new DirectoryInfo(Server.MapPath("~/downloadstuff"));
        int i = 0;
        foreach(FileInfo fi in di.GetFiles())
        {
            HyperLink HL = new HyperLink();
            HL.ID = "HyperLink" + i++;
            HL.Text = fi.Name;
            HL.NavigateUrl = "downloading.aspx?file="+fi.Name;
            Page.Controls.Add(HL);
            Page.Controls.Add(new LiteralControl("<br/>"));
        }
    }

 downloading.aspx:

    using System.IO;
    using System.Threading;

    protected void Page_Load(object sender, EventArgs e)
    {
        string filename = Request["file"].ToString();
        fileDownload(filename, Server.MapPath("~/downloadstuff/"+filename));
    }
    private void fileDownload(string fileName, string fileUrl)
    {
        Page.Response.Clear();
        bool success = ResponseFile(Page.Request, Page.Response, fileName, fileUrl, 1024000);
        if (!success)
            Response.Write("Downloading Error!");
        Page.Response.End();

    }
    public static bool ResponseFile(HttpRequest _Request, HttpResponse _Response, string _fileName, string _fullPath, long _speed)
    {
        try
        {
            FileStream myFile = new FileStream(_fullPath, FileMode.Open, FileAccess.Read, FileShare.ReadWrite);
            BinaryReader br = new BinaryReader(myFile);
            try
            {
                _Response.AddHeader("Accept-Ranges", "bytes");
                _Response.Buffer = false;
                long fileLength = myFile.Length;
                long startBytes = 0;

                int pack = 10240; //10K bytes
                int sleep = (int)Math.Floor((double)(1000 * pack / _speed)) + 1;
                if (_Request.Headers["Range"] != null)
                {
                    _Response.StatusCode = 206;
                    string[] range = _Request.Headers["Range"].Split(new char[] { '=', '-' });
                    startBytes = Convert.ToInt64(range[1]);
                }
                _Response.AddHeader("Content-Length", (fileLength - startBytes).ToString());
                if (startBytes != 0)
                {
                    _Response.AddHeader("Content-Range", string.Format(" bytes {0}-{1}/{2}", startBytes, fileLength - 1, fileLength));
                }
                _Response.AddHeader("Connection", "Keep-Alive");
                _Response.ContentType = "application/octet-stream";
                _Response.AddHeader("Content-Disposition", "attachment;filename=" + HttpUtility.UrlEncode(_fileName, System.Text.Encoding.UTF8));

                br.BaseStream.Seek(startBytes, SeekOrigin.Begin);
                int maxCount = (int)Math.Floor((double)((fileLength - startBytes) / pack)) + 1;

                for (int i = 0; i < maxCount; i++)
                {
                    if (_Response.IsClientConnected)
                    {
                        _Response.BinaryWrite(br.ReadBytes(pack));
                        Thread.Sleep(sleep);
                    }
                    else
                    {
                        i = maxCount;
                    }
                }
            }
            catch
            {
                return false;
            }
            finally
            {
                br.Close();
                myFile.Close();
            }
        }
        catch
        {
            return false;
        }
        return true;
    }

 Hope it helps.