I have a grid where I need all of the child records to be open when the page loads. I've set that hierarchy default expanded property so that the records are open, but the child records do not diplay any data. I'm wondering how to populate the child records based on their parent records?
Have you set the ParentTableRelation for the hierarchical Grid? Go through the following online demo where the detail table is populated based on the parent records. Three-level hierarchy
Give a try with the LiveDemo application that comes along with downloaded dll. Free Trials RadControls_for_ASP.NET_AJAX_2008_3_1314_trial --> Live Demos --> Grid --> Examples --> Hierarchy --> ThreeLevel