public void CreateCSV(DataTable dt, string fileName, HttpContext context)
        {
            StringBuilder csvDoc = new StringBuilder();
            string strTitle = string.Empty;
            for (int i = 0; i <= dt.Columns.Count - 1; i++)
            {
                strTitle += "\"" + dt.Columns[i].ColumnName + "\"";
                strTitle += ",";
            }
            strTitle.Substring(0,strTitle.Length-1); 
            csvDoc.AppendLine(strTitle);
             string strValue = string.Empty;
            foreach (DataRow dr in dt.Rows)
            {
                strValue = string.Empty;
                for (int i = 0; i <= dt.Columns.Count - 1; i++)
                {
                    strValue+=("\"" + dr[i].ToString().Replace("'", "''").Replace(",", "，") + "\"");
                    strValue += (",");
                }
                strValue.Substring(0,strValue.Length - 1);
                csvDoc.AppendLine(strValue);
            }
            byte[] strdata = System.Text.Encoding.Default.GetBytes(csvDoc.ToString());
            context.Response.ContentType = "application/octet-stream";
            context.Response.AddHeader("Content-Disposition", "attachment; filename=" + HttpUtility.UrlEncode(fileName, System.Text.Encoding.UTF8));
            context.Response.BinaryWrite(strdata);
            context.Response.Flush();
            context.Response.End();
         }