private void button1_Click(object sender, EventArgs e)
{
    if (folderBrowserDialog1.ShowDialog() == DialogResult.OK)
    {
        string foldPath = folderBrowserDialog1.SelectedPath;
        MessageBox.Show("已选择文件夹:" + foldPath, "选择文件夹提示", MessageBoxButtons.OK, MessageBoxIcon.Information);
        //获取该目录下的文件
         string[] files = System.IO.Directory.GetFiles(@foldPath+"\\", "*.txt", System.IO.SearchOption.TopDirectoryOnly);
        foreach (var f in files)
        {
            Console.WriteLine(f);
        }
    }
}