ASP.Net FileDownload : Access Denied error in IIS

Hi

     I have an issue while downloading files from a folder.In my application,i have to upload files to a particular folder inside my solution. I dint face any issues while uploading the files to the folder. But while downloading the file from the folder i get an error Access to path 'C:\FolderPath' is denied. I am using windows 7.

Below is the coding for download

protected void radgrdDocumnet_ItemCommand(object sender, GridCommandEventArgs e)
        {

            if (e.Item is GridDataItem)
            {
                GridDataItem item = e.Item as GridDataItem;

                string id = userProcess.Encrypt(item.OwnerTableView.DataKeyValues[item.ItemIndex]["ID"].ToString());

if (e.CommandName == "download")
                {
                    System.IO.FileStream fs = null;
                    fs = System.IO.File.Open(Server.MapPath("~/MyFiles"), System.IO.FileMode.Open);
                    byte[] btFile = new byte[fs.Length];
                    fs.Read(btFile, 0, Convert.ToInt32(fs.Length));

                    fs.Close();

                    // Response.AddHeader("Content-disposition", "attachment; filename=" + fileName);
                    Response.ContentType = "application/octet-stream";
                    Response.BinaryWrite(btFile);
                    Response.End();
                    fs = null;


                }
            }
        }