Is your document refresh required before you get the exception?
but once i maximize/minimize my application form or move the scrollbars inthe document , the block disappears…
OK, so the problem is in the “refresh” implementation. Please check that you are creating your blocks and adding them to layers that belong to your document being displayed by your view.
I included the initialization statement which u mentioned…but its not working.
You still haven’t described precisely what happens when the user double-clicks on a node. Are you making some layers visible / invisible? Are you adding new objects on other layers? What happens when the user double-clicks the same node several times?
OK, I have updated http://www.nwoods.com/forum/uploads/BlockLayers.zip to demonstrate what I think you want to do. It just creates one child per node, though. There are CheckBoxes so you can show/hide each GoLayer. I have added a link from each parent Block to its child Block, for clarity.