怎么遍历文件夹下面所有文件？

  foldPath = dialog.SelectedPath;

                this.label4.Text = foldPath;

                

                DirectoryInfo TheFolder = new DirectoryInfo(foldPath);

                fileName = Path.GetFileName(dialog.SelectedPath);//获取当前打开文件夹名称

                foreach (FileInfo NextFile in TheFolder.GetFiles())

                {

                    this.listBox1.Items.Add(NextFile.Name);

                    string tempStr = File.ReadAllText(NextFile.FullName, Encoding.GetEncoding("GB2312"));//读取txt内容 

                    this.richTextBox1.Text = tempStr;

                }

这个方法就只能遍历第一个文件的所有内容，我用listBox1显示出了所有的文件名称，请问下要怎么遍历全部文件呢？
------解决方案--------------------
http://www.cnblogs.com/qianqianfy/archive/2009/07/08/1518974.html
------解决方案--------------------

        private void ScanAllFolder(string pathName)

         {

             try

             {

                 if (!Directory.Exists(pathName))

                 {

                     return;

                 }

 

                 DirectoryInfo processDirectory = new DirectoryInfo(pathName);

 

                 FileSystemInfo[] fileSystemInfos = processDirectory.GetFileSystemInfos();

 

                 foreach (FileSystemInfo fileSystemInfo in fileSystemInfos)

                 {

                     if (fileSystemInfo is DirectoryInfo &&