Merge pull request #1 from SyncfusionExamples/ES-975464

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

Author: vijayarasan

README.md

@@ -1,5 +1,36 @@
-# How to populate child nodes asynchronously in uwp treegrid?
+# How to Populate Child Nodes Asynchronously in UWP TreeGrid?
 
-## About the example
+This example illustrates how to populate child nodes asynchronously in [UWP TreeGrid](https://www.syncfusion.com/uwp-ui-controls/treegrid) (SfTreeGrid).
 
-This example illustrates how to populate child nodes asynchronously in uwp treegrid
+You can populate the child nodes asynchronously using **async** and **await** at runtime when retrieving data from web services or any database. This can be performed by [PopulateChildNodes](https://help.syncfusion.com/cr/uwp/Syncfusion.UI.Xaml.TreeGrid.TreeNode.html#Syncfusion_UI_Xaml_TreeGrid_TreeNode_PopulateChildNodes_System_Collections_Generic_IEnumerable_System_Object__) method from [TreeGridRequestTreeItemsEventArgs.ParentNode](https://help.syncfusion.com/cr/uwp/Syncfusion.UI.Xaml.TreeGrid.TreeGridRequestTreeItemsEventArgs.html#Syncfusion_UI_Xaml_TreeGrid_TreeGridRequestTreeItemsEventArgs_ParentNode) property.
+
+``` c#
+private async void TreeGrid_RequestTreeItems(object sender, TreeGridRequestTreeItemsEventArgs args)
+{
+    if (args.ParentItem == null)
+    {
+        args.ChildItems =  viewModel.Employees.Where(x => x.ReportsTo == -1);
+    }
+    //if ParentItem not null, then set args.ChildList to the child items for the given ParentItem.
+    else
+    {
+        EmployeeInfo ems = args.ParentItem as EmployeeInfo;
+              
+        if (ems != null)
+        {
+            await Task.Run(async () =>
+            {
+                await this.treeGrid.Dispatcher.RunAsync(CoreDispatcherPriority.High, async() =>
+                {
+                    //Get the child items with time delay
+                    var childItems = await viewModel.GetEmployees(ems.ID);
+
+                    //Populate the child nodes based on the child items
+                    args.ParentNode.PopulateChildNodes(childItems);
+                });
+                       
+            });
+        }
+    }
+}
+```