private void button2_Click(object sender, EventArgs e)
{
    FolderBrowserDialog dlg = new FolderBrowserDialog();
    dlg.SelectedPath = Path.GetFullPath(".");
    if (dlg.ShowDialog() == DialogResult.OK)
    {
        string path = dlg.SelectedPath;
        MessageBox.Show("选中了:" + path);
    }
}