FileExplorer使用treeview

Question

我有ImageList和TreeView。我创建了一个包含三个文件夹的文件夹，每个文件夹包含三个文本文件。当我开始调试它时，它只有根文件夹，无法展开它以查看其他文件夹和文件。关于如何解决它的任何想法。

using System.IO;

namespace WindowsFormsApplication1
{
  public partial class Form1 : Form
  {
    public Form1()
    {
        InitializeComponent();
    }

    DirectoryInfo directoryinfo = new DirectoryInfo(@"C:\Users\zaid\Documents\Visual Studio 2010\Projects\file_explorer");
    private void Form1_Load(object sender, EventArgs e)
    {
        if (Directory.Exists("file_explorer"))
        {
            try
            {
                DirectoryInfo[] directories = directoryinfo.GetDirectories();
                if (directories.Length > 0)
                {
                    foreach (DirectoryInfo directory in directories)
                    {
                        TreeNode node = treeView1.Nodes[0].Nodes.Add(directory.Name);
                        node.ImageIndex = 1;
                        foreach (FileInfo file in directory.GetFiles())
                        {
                            if (file.Exists)
                            {
                                TreeNode nodes = treeView1.Nodes[0].Nodes[node.Index].Nodes.Add(file.Name);
                                nodes.ImageIndex = 2;
                            }
                        }
                    }
                }
            }
            catch (Exception ex)
            {
                MessageBox.Show(ex.Message);
            }
        }
    }
}

}