Tree view Issue in c#

Question

Actually My Question is: I have a treeview that displaying the logical drivers with checkboxes, If I select C: drive It should be select all the folders and subfolders. If I Deselect the C: drive It should deselect all the folders and subfolders within subfolders...

My Code :

    private void Form2_Load(object sender, EventArgs e)
    {
        treeView1.CheckBoxes = true;
        foreach (TreeNode node in treeView1.Nodes)
        {
            node.Checked = true;
        }

        string[] drives = Environment.GetLogicalDrives();

        foreach (string drive in drives)
        {
           // treeView1.Nodes[0].Nodes[1].Checked = true;
            DriveInfo di = new DriveInfo(drive);
            int driveImage;

            switch (di.DriveType)   
            {
                case DriveType.CDRom:
                    driveImage = 3;
                    break;
                case DriveType.Network:
                    driveImage = 6;
                    break;
                case DriveType.NoRootDirectory:
                    driveImage = 8;
                    break;
                case DriveType.Unknown:
                    driveImage = 8;
                    break;
                default:
                    driveImage = 2;
                    break;
            }

            TreeNode node = new TreeNode(drive.Substring(0, 1), driveImage, driveImage);
            node.Tag = drive;


            if (di.IsReady == true)
                node.Nodes.Add("...");

            treeView1.Nodes.Add(node);


        }

        foreach (TreeNode node in treeView1.Nodes)
        {
            node.Checked = true;
        }
    }


    private void treeView1_BeforeExpand(object sender, TreeViewCancelEventArgs e)
    {


        if (e.Node.Nodes.Count > 0)
        {
            if (e.Node.Nodes[0].Text == "..." && e.Node.Nodes[0].Tag == null)
            {
                e.Node.Nodes.Clear();


                string[] dirs = Directory.GetDirectories(e.Node.Tag.ToString());

                foreach (string dir in dirs)

                {
                    DirectoryInfo di = new DirectoryInfo(dir);
                    TreeNode node = new TreeNode(di.Name, 0, 1);
                    node.Checked = true;

                    try
                    {
                        node.Tag = dir;  


                        if (di.GetDirectories().Count() > 0)
                            node.Nodes.Add(null, "...", 0, 0);
                    }
                    catch (UnauthorizedAccessException)
                    {
                        node.ImageIndex = 12;
                        node.SelectedImageIndex = 12;
                    }
                    catch (Exception ex)
                    {
                        MessageBox.Show(ex.Message, "DirectoryLister", MessageBoxButtons.OK,
                            MessageBoxIcon.Error);
                    }
                    finally
                    {
                        e.Node.Nodes.Add(node);
                    }
                }

            }
        }

    }

    private void treeView1_AfterCheck(object sender, TreeViewEventArgs e)
    {
        foreach (TreeNode childNode in e.Node.Nodes)
        {
            childNode.Checked = e.Node.Checked;

        }
    }

    private void button1_Click(object sender, EventArgs e)
    {
        foreach (TreeNode node in treeView1.Nodes)
        {
            node.Checked = true;

        }

     }

    private void button2_Click(object sender, EventArgs e)
    {
        foreach (TreeNode node in treeView1.Nodes)
        {
             node.Checked = false;             
        }
    }

    private void button3_Click(object sender, EventArgs e)
    {
        Form3 f3 = new Form3();
        f3.ShowDialog();

    }


}

}