ES-975464 - Resolve the ReadMe issue in this sample repository

README.md

@@ -1,2 +1,31 @@
-# How to load data on demand using events in winui treegrid?
-This examples describes how to load data on demand using events in winui treegrid.
+# How to load data on demand using events in WinUI TreeGrid
+
+This examples describes how to load data on demand using events in [WinUI TreeGrid](https://www.syncfusion.com/winui-controls/treegrid) (SfTreeGrid).
+
+SfTreeGrid supports to load the data in on-demand through [SfTreeGrid.RequestTreeItems](https://help.syncfusion.com/cr/winui/Syncfusion.UI.Xaml.TreeGrid.SfTreeGrid.html#Syncfusion_UI_Xaml_TreeGrid_SfTreeGrid_RequestTreeItems) event. `RequestTreeItems` event is triggered at the time of loading and when user expand any node at runtime. SfTreeGrid gets the root and leaf nodes through this event handler.
+
+`TreeGridRequestTreeItemsEventArgs.ParentItem` denotes the data object looking for its child nodes. If it is null, it denotes SfTreeGrid requesting root nodes.
+
+In the below example SfTreeGrid is populated through `SfTreeGrid.RequestTreeItems` instead of setting [SfTreeGrid.ItemsSource](https://help.syncfusion.com/cr/winui/Syncfusion.UI.Xaml.TreeGrid.SfTreeGrid.html#Syncfusion_UI_Xaml_TreeGrid_SfTreeGrid_ItemsSource).
+
+``` csharp
+treeGrid.RequestTreeItems += TreeGrid_RequestTreeItems;
+
+private void TreeGrid_RequestTreeItems(object sender, TreeGridRequestTreeItemsEventArgs e)
+{
+    if (e.ParentItem == null)
+    {
+        //get the root list - get all employees who have no boss 
+        e.ChildItems = (this.treeGrid.DataContext as ViewModel).EmployeeDetails.Where(x => x.ReportsTo == -1); //get all employees whose boss's id is -1 (no boss)
+    }
+    else //if ParentItem not null, then set args.ChildList to the child items for the given ParentItem.
+    {   //get the children of the parent object
+        EmployeeInfo emp = e.ParentItem as EmployeeInfo;
+        if (emp != null)
+        {
+            //get all employees that report to the parent employee
+            e.ChildItems = (this.treeGrid.DataContext as ViewModel).GetReportees(emp.ID);
+        }
+    }
+}
+```