Update Folder All file name in C#

DirectoryInfo d = new DirectoryInfo(Server.MapPath("~/RUpload/"));
       FileInfo[] infos = d.GetFiles();
       string extension;

       foreach (FileInfo f in infos)
       {
           try
           {
               extension = Path.GetExtension(f.FullName);
               String[] strf = f.FullName.Split('\\');
               objBLLM_EntranceDetails.Sptype = 2;
               //objBLLM_EntranceDetails.MED_Document = strf[strf.Length - 1].Replace(extension, "");
               objBLLM_EntranceDetails.MED_Document = strf[strf.Length - 1];
               DataSet objds = objBLLM_EntranceDetails.ExecuteDataset(objBLLM_EntranceDetails);
               if (objds.Tables[0].Rows.Count > 0)
               {
                   try
                   {
                       File.Move(f.FullName, f.FullName.ToString().Replace(objds.Tables[0].Rows[0]["CSign"].ToString(),objds.Tables[0].Rows[0]["FromNo"].ToString() + extension));
                   }
                   catch (Exception)
                   {

                   }


               }
           }
           catch (Exception)
           {


           }
       }