How do I set an image for some but not all nodes in a TreeView?

Question

I have a TreeView windows forms control with an ImageList, and I want some of the nodes to display images, but I want the others to not have images.

I don't want a blank space where the image should be. I don't want an image that looks like the lines that the TreeView would draw if it didn't have an ImageList. How do I get it to draw images for some items and not others, without resorting to clumsy hacks like that?

Answer 1

I tried this once and I don't think it is possible.

If you try to set both ImageKey and ImageIndex to "not set" values the control just defaults ImageIndex to 0. The following code:

treeView.ImageKey = "Value";
Debug.WriteLine(treeView.ImageIndex);
treeView.ImageKey = null;
Debug.WriteLine(treeView.ImageIndex);
treeView.ImageIndex = -1;
Debug.WriteLine(treeView.ImageIndex);

Produces output:

-1
0
0

This kind of tells you that the control developers wanted to make sure that there was always a default image. That just leaves you with the hack options I'm afraid.

Answer 2

You need to set imageIndex and selectedImageIndex to a number that is higher than the number of values in your ImageList. For example, if you create this node and add it to your treeview:

TreeNode node1 = new TreeNode(string.Empty, 12, 12); // imageList1.Count = 5

you will have an invisible TreeNode inserted into your TreeView. I changed the background color of my TreeView and it was still invisible.

(I googled this for some time, and I eventually found the answer here: http://www.tech-archive.net/Archive/DotNet/microsoft.public.dotnet.framework.windowsforms/2006-09/msg00322.html)