Cannot set icon for node of treeview
===

I have a treeview and a imageList which contain 1 icon (folder.ico), I want to set icon only for root node, child node will don't have icon, so I try to set image index for child node but it have some problem, look the picture:
![enter image description here][1]


  [1]: http://i.stack.imgur.com/znZ6C.png

My code:

            ImageList imageList = new ImageList();
            imageList.Images.Add(Image.FromFile(System.AppDomain.CurrentDomain.BaseDirectory.Replace("\\bin\\Debug\\","") + "\\Images\\folder.ico"), Color.Transparent);
            treeView1.ImageList = imageList;
            foreach (TreeNode node in treeView1.Nodes)
            {
                foreach (TreeNode node2 in node.Nodes)
                {
                    node2.ImageIndex = 100;
                    node2.SelectedImageIndex = 100;
                }
            }

Thanks