C#.NET讀取一個文件目錄下所有excel文件

 string defaultfilePath = "";

        private void btn_OpenFile_Click(object sender, EventArgs e)
        {
            FolderBrowserDialog dialog = new FolderBrowserDialog();
            dialog.ShowNewFolderButton = false;
            dialog.Description = "請選擇文件路徑";
            if (defaultfilePath != "")
            {
                //設置此次默認目錄為上一次選中目錄  
                dialog.SelectedPath = defaultfilePath;
            }
            DialogResult result = dialog.ShowDialog();
            if (result == DialogResult.OK || result == DialogResult.Yes)
            {
                string foldPath = dialog.SelectedPath;
                txt_Directory.Text = defaultfilePath = foldPath;
                string[] files = Directory.GetFiles(txt_Directory.Text + @"\", "*.xls");
                foreach (string file in files)
                {
                    MessageBox.Show(file);
                }
            }
        }