c#无法在有其他文件的目录中创建文件

谁能帮帮我，我刚学习c#大约2个月，我有这个问题，我正在构建一个从临时文件过滤数据的类，并在目录内的新TXT文件中创建结果，如果目录是空的，也不在同一日期，它会完美地构建，如果在同一日期有另一个文件，它应该创建增加lastname的最后数字。

我的问题是，当我运行代码时，如果目录中有相同日期的文件，则不会创建，那么结果应该是这样的:

• C: ' result_2014051301.txt
• C: ' result_2014051401.txt

• C:'result_2014051402.txt <—Failed, it is not .2014051401.txt

   class Entity2
   {
      public Entity2()
      {
         string fileTemp = "DEFAULT.temp";
         string indexD = Properties.Settings.Default.ChIndex2D;
         string indexC = Properties.Settings.Default.ChIndex2C;
         string indexS = Properties.Settings.Default.ChIndex2S;
         string tempPath = AppDomain.CurrentDomain.BaseDirectory;
         string targetPath = Properties.Settings.Default.ExtractALL_DIR;
         string SourceFile = Path.Combine(tempPath, fileTemp);
         string tempFileX = Path.GetTempFileName();
         if (!System.IO.Directory.Exists(targetPath))
         {
             System.Windows.Forms.MessageBox.Show("Error missing .temp", "Message Box");
         }
         else
         {
             string ext = ".txt";
             int sequence = 0;
             DateTime dateFileName = DateTime.Today;
             string discode = Properties.Settings.Default.ChannelID_2;
             string filename = discode + "_" + dateFileName.ToString("yyyyMMdd");
             string pathX = Properties.Settings.Default.ExtractALL_DIR + @"/Channel2";
             if (!Directory.Exists(pathX))
             {
                 Directory.CreateDirectory(pathX);
             }
             string[] files = Directory.GetFiles(pathX, filename + "*.txt", SearchOption.TopDirectoryOnly);
             if (files.Length > 0)
             {
                 Array.Sort(files);
                 string lastFilename = files[files.Length - 1];
                 sequence = Int32.Parse(lastFilename.Substring(0, lastFilename.Length - 4).Replace(pathX + filename, ""));
             }
             sequence++;
             string newFileName = filename + sequence.ToString().PadLeft(2, '0') + ext;
             string DestFile = Path.Combine(pathX, newFileName);
             using (var ab = new StreamReader(SourceFile))
             using (var cd = new StreamWriter(DestFile))
             {
                string lineX;
                while ((lineX = ab.ReadLine()) != null)
                {
                  if (lineX.LastIndexOf("100", 3) != -1 || lineX.LastIndexOf("MGR", 15) != -1 || lineX.LastIndexOf(indexC, 15) != -1)
                  {
                      lineX = lineX.Replace(indexD, "");
                      lineX = lineX.Replace("DEFAULT", discode);
                      if (lineX.LastIndexOf("800", 3) != -1)
                      {
                          lineX = lineX.Replace(indexS, "");
                      }
                      cd.WriteLine(lineX);
                  }
                }
             }
         }
      }
   }
  

Int32.Parse(lastFilename.Substring(0, lastFilename.Length - 4).Replace(pathX + filename, ""));