我的C#代码显示文件，但它必须将目录显示给

using System;
using System.IO;
using System.Windows.Forms;

namespace FileSelector
{
    public partial class MainForm : Form
    {
        public MainForm()
        {
            InitializeComponent();
        }

        private void selectFileButton_Click(object sender, EventArgs e)
        {
            OpenFileDialog openFileDialog = new OpenFileDialog();
            openFileDialog.InitialDirectory = "C:\\"; // 设置初始目录
            openFileDialog.Filter = "All files (*.*)|*.*"; // 设置文件过滤器

            if (openFileDialog.ShowDialog() == DialogResult.OK)
            {
                string filePath = openFileDialog.FileName;
                string directoryPath = Path.GetDirectoryName(filePath);

                directoryTextBox.Text = directoryPath;
            }
        }
    }
}