Enhanced BrowseForFolder styled TreeView

private DirectoryInfo[] SortDirArray( DirectoryInfo[] unsorted )
{
    try
    {
        Array.Sort<DirectoryInfo>( unsorted, new
            Comparison<DirectoryInfo>( delegate( DirectoryInfo d1, DirectoryInfo d2 )
                  {
                       return string.Compare( d1.Name, d2.Name );
                     } 
                  ) 
               );
    }
    catch
    {
    }
    return unsorted;
}
 
public virtual void RequestSubDirs(TreeViewFolderBrowserHelper helper, TreeNodePath parent, TreeViewCancelEventArgs e)
{
	if(parent.Path==null) return;
	//
	DirectoryInfo directory = new DirectoryInfo(parent.Path);	
	// check persmission
	new System.Security.Permissions.FileIOPermission(System.Security.Permissions.FileIOPermissionAccess.PathDiscovery, directory.FullName).Demand();										
	//					
	foreach( DirectoryInfo dir in SortDirArray(directory.GetDirectories()))
	{
		if ((dir.Attributes & System.IO.FileAttributes.System) == System.IO.FileAttributes.System)
		{
			continue;
		}
		if ((dir.Attributes & System.IO.FileAttributes.Hidden) == System.IO.FileAttributes.Hidden)
		{
			continue;
		}
		TreeNodePath newNode = this.CreateTreeNode(helper, dir.Name,dir.FullName,false,((helper.TreeView.CheckboxBehaviorMode != CheckboxBehaviorMode.None) && (parent.Checked)),false);
		parent.Nodes.Add(newNode);						
		//
		try
		{
			if(dir.GetDirectories().GetLength(0) > 0)
			{
				newNode.AddDummyNode();
			}
		} 
		catch{}						
	}			
}

// is it allowed to check item ? 
//if ((this.CheckboxBehaviorMode==CheckboxBehaviorMode.RecursiveChecked) & (!check) & (e.Node.Parent!=null) 
//   && (e.Node.Parent.Checked))
//{
//   e.Cancel = true;
//   base.OnBeforeCheck(e);
//   return;
//}

public virtual void Populate(List<string> path_list)

        private void fill()
        {
            tvfb.Populate();
 
            DataTable dt = Base.Select(@"SELECT * FROM CheckedFolder;"); // I save tvfb.SelectedDirectories to DB on FormClosing. You can fill the list any way you want.
            List<string> path_list = new List<string>();
            foreach (DataRow dr in dt.Rows)
                path_list.Add(dr["Path"].ToString());
 
            path_list.Sort();
            checkFolders(path_list);
        }
 
        private void checkFolders(List<string> path_list)
        {
            foreach (TreeNodePath tn in tvfb.Nodes)
            {
                foreach (string s in path_list) // if the subdir has to be checked expands the parent node
                {
                    if (tn.Path == Regex.Match(s, @"[A-Z]:\\(?=.)").Value)
                    {
                        tn.Expand();
                        break;
                    }
                }
 
                if (path_list.Contains(tn.Path))
                    tn.Checked = true;
 
                checkTreeNode(tn, path_list);
            }
        }
 
        private void checkTreeNode(TreeNodePath tnParent, List<string> path_list)
        {
            foreach (TreeNodePath tn in tnParent.Nodes)
            {
                string regex = @"[A-Z]:";
                regex += regexAddSubDir(tn); // modifies the regex depending on node depth (number of parents)
                regex += @"(?=\\)";
 
                foreach (string s in path_list) // if the subdir has to be checked expands the parent node
                {
                    if (tn.Path == Regex.Match(s, regex).Value)
                    {
                        tn.Expand();
                        break;
                    }
                }
 
                if (path_list.Contains(tn.Path))
                    tn.Checked = true;
 
                checkTreeNode(tn, path_list);
            }
        }
 
        private string regexAddSubDir(TreeNodePath tn)
        {
            string ret = "";
 
            if (tn.Parent != null) // modifies the regex depending on node depth (number of parents)
            {
                ret += @"\\([^\\]+)";
                ret += regexAddSubDir((TreeNodePath)tn.Parent);
            }
 
            return ret;
        }

myTreeView.SelectedDirectories

tvfb.Populate();
StringCollection sc = new StringCollection();
sc.Add("C:\\Program Files");
tvfb.SelectedDirectories = sc;

/// <summary>
        /// Clears the TreeView and popluates the root level and all selected folders.
        /// </summary>
        /// <param name="path_list"></param>The paths of the folder sthat should be checked after population.
        /// <param name="expandNodes"></param>if True, expands the parent nodes of selected folders after population.
        public virtual void Populate(StringCollection path_list, bool expandNodes)
        {
            Populate();
 
            foreach (TreeNodePath tn in this.Nodes)
            {
                foreach (string s in path_list) // if the subdir has to be checked expands the parent node   
                {
                    if (tn.Path == Regex.Match(s, @"[A-Z]:\\(?=.)").Value)
                    {
                        if (expandNodes)
                            tn.Expand();
                        else
                        {
                            try { GetSubDirs(tn, new TreeViewCancelEventArgs(null, false, TreeViewAction.ByMouse)); }
                            catch { }
                        }
                        break;
                    }
                }
 
                if (path_list.Contains(tn.Path))
                    tn.Checked = true;
                checkTreeNode(tn, path_list, expandNodes);
            }
        }
 
        private void checkTreeNode(TreeNodePath tnParent, StringCollection path_list, bool expandNodes)
        {
            foreach (TreeNodePath tn in tnParent.Nodes)
            {
                string regex = @"[A-Z]:";
                regex += regexAddSubDir(tn); // modifies the regex depending on node depth (number of parents)        
                regex += @"(?=\\)"; foreach (string s in path_list) // if the subdir has to be checked expands the parent node    
                {
                    if (tn.Path == Regex.Match(s, regex).Value)
                    {
                        if (expandNodes)
                            tn.Expand();
                        else
                        {
                            try { GetSubDirs(tn, new TreeViewCancelEventArgs(null, false, TreeViewAction.ByMouse)); }
                            catch { }
                        }
                        break;
                    }
                }
 
                if (path_list.Contains(tn.Path))
                    tn.Checked = true;
 
                checkTreeNode(tn, path_list, expandNodes);
            }
        }
 
        private string regexAddSubDir(TreeNodePath tn)
        {
            string ret = ""; if (tn.Parent != null) // modifies the regex depending on node depth (number of parents)      
            { ret += @"\\([^\\]+)"; ret += regexAddSubDir((TreeNodePath)tn.Parent); }
            return ret;
        }

TreeNodePath node = e.Node as TreeNodePath;
            try
            {
                GetSubDirs(node, e);
            }
            catch {}