C# 文件重命名

 /// <summary>
        /// 把剩余的图片和txt重新命名
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        private void btnFinish_Click(object sender, EventArgs e)
        {
            DirectoryInfo dir = new DirectoryInfo(_path);
            FileInfo[] files = dir.GetFiles();
            if (files.Count() == 0)
            {
                empty = true;
                MessageBox.Show("File is Empty!");
                pictureBox1.Refresh();
                return;
            }
            int txtFile = 1;
            int imaIndex = 1;
            foreach (FileInfo item in files)
            {
                if (item.Extension == ".bmp")
                {
                    File.Move(item.FullName,_path+"\\"+imaIndex.ToString()+".bmp");
                    imaIndex++;

                }
                else
                {
                    File.Move(item.FullName,_path+"\\"+ txtFile.ToString()+".txt");
                    txtFile++;
                }

            }
            MessageBox.Show("Order is finished !");
            Initial(trackBar1.Value);
        }