I’m writing a silverlight app that queries a web service to populate a tree control. Each element will have at least 2 levels of children, so something like this:
a
+-b
+-c
d
+-g
+-h
e
+-i
+-j
f
+-k
+-l
The web service API is such that I can only get one level of child nodes at a time, so the first trip, I can get a,d,e,f. To get b,g,i,k, I have to make 4 trips. Similarly, I have to make 4 more trips to get c,h,j,l. (The service does actually allow me to get all the nodes in one trip, but it doesn’t give me parent-child relationships along with it :-()
My question is this: should I make the user wait for a while up front while I get all the nodes for the tree view, or should I just get the top few nodes, and get the other nodes on-demand, or in a background task? Also, the nodes can change asynchronously, so if I get all the nodes up front, I’ll need a “refresh” button for the treeview, and if I do it on demand, I’ll have to have a caching strategy.
Which is best for the user?
A compromise where you load the first level up front and then load the remaining items in the background overridden by on-demand as required. If you load the nodes breadth first (e.g. a,d,e,f then b,g,i,k) rather than depth first (e.g. a,d,e,f followed by b,c) you can redirect your loading to be focused on the most recently expanded node.