ContextualHelp revit api
ContextualHelp hlp = new ContextualHelp(ContextualHelpType.Url, hlppath);
bone.SetContextualHelp(hlp);
btwo.SetContextualHelp(hlp);
bthree.SetContextualHelp(hlp);
SplitButtonData sb1 = new SplitButtonData("splitButton1", "Split");
sb1.SetContextualHelp(hlp);
SplitButton sb = panel.AddItem(sb1) as SplitButton;
sb.AddPushButton(bone);
sb.AddPushButton(btwo);
sb.AddPushButton(bthree);
sb.SetContextualHelp(hlp);