OpenFileDialog 只提取对话框路径

Question

用OpenFileDialog时,一定要选择一个文件才可以点击对话框上的"打开" 按钮.现在只想实现一个文件备份功能,只提取对话框提取当前文件夹路径作为备份路径.如何做到不用点击点击对话框上的"打开" 按钮就可以提取当前路径 后显示对一个textbox里?
OpenFileDialog openFileDialog = new OpenFileDialog();
            openFileDialog.InitialDirectory = "c:\\";
            openFileDialog.Filter = "Access文件|*.mdb|所有文件|*.*";
            openFileDialog.RestoreDirectory = true;
            openFileDialog.FilterIndex = 1;
            if (openFileDialog.ShowDialog() == DialogResult.OK)
            {
                this.txtBackUp.Text = openFileDialog.FileName;//如何做到在对话框里不用选择文件即可提取路径到TEXTBOX里?
            }