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

Author: SreemonPremkumarM

README.md

@@ -1,5 +1,106 @@
-# How to merge cells in a row in wpf treegrid?
-This example explains how to merge cells in a row in wpf treegrid
+# How to merge cells in a row in wpf treegrid
+
+This example explains how to merge cells in a row in [WPF TreeGrid](https://www.syncfusion.com/wpf-controls/treegrid).
+
+You can merge the entire column parent node using `TreeGridCoveredCellInfo`.
+
+### XAML
+
+``` xml
+<syncfusion:SfTreeGrid Name="treeGrid"
+                       ItemsSource="{Binding EmployeeDetails}"
+                       QueryCoveredRange="treeGrid_QueryCoveredRange"
+                       SelectionMode="Single"
+                       NavigationMode="Cell">
+```
+
+### C#
+
+``` c#
+public delegate void TreeGridRequestTreeItemsHandler(object sender, RoutedEventArgs args);
+
+/// <summary>
+///  Handles the cell merging in SfTreeGrid.
+/// </summary>
+public class QueryCoveredRangeBehavior : Behavior<SfTreeGrid>
+{
+    /// <summary>
+    /// Called after the behavior is attached to an AssociatedObject.
+    /// </summary>
+    /// <remarks>Override this to hook up functionality to the AssociatedObject.</remarks>
+    protected override void OnAttached()
+    {
+        var loader= new TreeGridRequestTreeItemsHandler(AssociatedObject_Loaded);
+        loader.Invoke(null, null);
+    }
+
+    public  void AssociatedObject_Loaded(object sender, RoutedEventArgs e)
+    {
+        this.AssociatedObject.QueryCoveredRange += AssociatedObject_QueryCoveredRange;
+    }
+       
+    public void AssociatedObject_QueryCoveredRange(object sender, TreeGridQueryCoveredRangeEventArgs e)
+    {
+        var treeNode = this.AssociatedObject.GetNodeAtRowIndex(e.RowColumnIndex.RowIndex);
+        if (treeNode != null && treeNode.HasChildNodes)
+        {
+            if (e.RowColumnIndex.ColumnIndex >= 1 && e.RowColumnIndex.ColumnIndex <= this.AssociatedObject.Columns.Count)
+            {
+                e.Range = new TreeGridCoveredCellInfo(0, this.AssociatedObject.Columns.Count, e.RowColumnIndex.RowIndex);
+                e.Handled = true;
+            }
+        }
+    }
+
+    /// <summary>
+    /// Calls when the behavior is being detached from its AssociatedObject, but before it has actually occurred.
+    /// </summary>
+    /// <remarks>Override this to unhook functionality from the AssociatedObject.</remarks>
+    protected override void OnDetaching()
+    {
+        base.OnDetaching();
+        this.AssociatedObject.Loaded -= AssociatedObject_Loaded;
+        this.AssociatedObject.QueryCoveredRange -= AssociatedObject_QueryCoveredRange;
+    }
+}
+
+class RequestTreeItemsBehavior : Behavior<SfTreeGrid>
+{
+    EmployeeRepository viewModel;
+
+    protected override void OnAttached()
+    {
+        base.OnAttached();
+        viewModel = this.AssociatedObject.DataContext as EmployeeRepository;
+        this.AssociatedObject.RequestTreeItems += AssociatedObject_RequestTreeItems;
+    }
+
+    void AssociatedObject_RequestTreeItems(object sender, TreeGridRequestTreeItemsEventArgs args)
+    {
+        if (args.ParentItem == null)
+        {
+            // Gets the root list - Gets all employees who have no boss.
+            args.ChildItems = EmployeeRepository.GetEmployees().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.
+        {   
+            // Gets the children of the parent object.
+            Employee emp = args.ParentItem as Employee;
+            if (emp != null)
+            {
+                // Gets all employees who report to the parent employee.
+                args.ChildItems = EmployeeRepository.GetEmployees().Where(x => x.ReportsTo == emp.Id);
+            }
+        }
+    }       
+
+    protected override void OnDetaching()
+    {
+        base.OnDetaching();
+        this.AssociatedObject.RequestTreeItems -= AssociatedObject_RequestTreeItems;
+    }
+}
+```
 
 Note:
 Supports cell merging from 17.2.0.28 version