实现效果:

知识运用:
Directory类的GetParent方法 //检索指定路径的付文件夹 包括绝对路径和相对路径
public static DirectoryInfo GetParent (string path)
实现代码:
private void button1_Click(object sender, EventArgs e)
{
FolderBrowserDialog FBDialog = new FolderBrowserDialog();
if(FBDialog.ShowDialog()==DialogResult.OK)
{
textBox1.Text=FBDialog.SelectedPath;
string str1=textBox1.Text;
string str2=Directory.GetParent(str1).FullName;
string myInfo="当前目录是: "+str1+Environment.NewLine+"上级目录是: "+str2;
label2.Text=myInfo;
}
}