private void button3_Click(object sender, EventArgs e)
        {
            FolderBrowserDialog dialog = new FolderBrowserDialog();
            dialog.Description = "请选择文件路径";
           
            if (dialog.ShowDialog() == DialogResult.OK)
            {
                string foldPath = dialog.SelectedPath;
                DirectoryInfo theFolder = new DirectoryInfo(foldPath);
                FileInfo[] dirInfo = theFolder.GetFiles();
                //遍历文件夹
                foreach (FileInfo file in dirInfo)
                {
                    MessageBox.Show(file.ToString());
                }
            }
        }