docs(treeview): clarify behavior

Author: marin-bratanov

_contentTemplates/treeview/basic-example.md

@@ -18,11 +18,8 @@
 		public bool HasChildren { get; set; }
 		public string Icon { get; set; }
 		public bool Expanded { get; set; }
-
-		public TreeItem()
-		{
-		}
 	}
+	
 	public IEnumerable<TreeItem> FlatData { get; set; }
 
 	protected override void OnInit()

components/treeview/data-binding/flat-data.md

@@ -18,6 +18,8 @@ Flat data means that the entire collection of treeview items is available at one
 
 The parent-child relationships are created through internal data in the model - the `ParentId` field which points to the `Id` of the item that will contain the current item. The root level has `null` for `ParentId`.
 
+You must also provide the correct value for the `HasChildren` field - for items that have children, you must set it to `true` so that the expand arrow is rendered.
+
 >caption Example of flat data in a treeview
 
 ````CSHTML

components/treeview/data-binding/hierarchical-data.md

@@ -14,9 +14,9 @@ This article explains how to bind the TreeView for Blazor to hierarchical data.
 @[template](/_contentTemplates/treeview/basic-example.md#data-binding-basics-link)
 
 
-Hierarchical data means that the collection child items is provided in a field of its parent's model. By default, this is the `Items` field.
+Hierarchical data means that the collection child items is provided in a field of its parent's model. By default, this is the `Items` field. If there are items for a certain node, it will have an expand icon. The `HasChildren` field can override this, however, but it is not required for hierarchical data binding.
 
-This lets you gather separate collections of data and/or use different models at each different level. Note that the data binding settings are per level, so a certain level will always use the same bindings, regardless of the model they represent and their parent.
+This approach of providing nodes lets you gather separate collections of data and/or use different models at each different level. Note that the data binding settings are per level, so a certain level will always use the same bindings, regardless of the model they represent and their parent.
 
 >caption Example of hierarchical data that uses different models for the parent and the child. Using different models is not required.
 
@@ -38,7 +38,6 @@ This lets you gather separate collections of data and/or use different models at
 		public string Category { get; set; }
 		public List<ProductItem> Products { get; set; }
 		public bool Expanded { get; set; }
-		public bool HasChildren { get; set; }
 	}
 
 	public class ProductItem
@@ -48,7 +47,6 @@ This lets you gather separate collections of data and/or use different models at
 		// they are not really used in this example and you would have a collection of child items too
 		// see the information about multiple data bindings earlier in this article on using them
 		public bool Expanded { get; set; }
-		public bool HasChildren { get; set; }
 	}
 
 
@@ -71,8 +69,7 @@ This lets you gather separate collections of data and/or use different models at
 		{
 			Category = "Category 1",
 			Expanded = true,
-			Products = firstCategoryProducts, // this is how child items are provided
-			HasChildren = firstCategoryProducts?.Count > 0, // set this depending on the presence of items in the child items collection
+			Products = firstCategoryProducts // this is how child items are provided
 
 		});
 

components/treeview/data-binding/overview.md

@@ -27,13 +27,13 @@ There are three modes of providing data to a treeview, and they all use the item
 
 The treeview items provide the following features that you control through the corresponding fields in their data binding:
 
-* `Id` - a unique identifier for the item. Required.
-* `ParentId` - identifies the parent to whom the item belongs. Needed only when binding to flat data. All items with the same `ParentId` will be rendered at the same level. For a root level item, this must be `null`.
+* `Id` - a unique identifier for the item. Required for binding to flat data.
+* `ParentId` - identifies the parent to whom the item belongs. Required only when binding to flat data. All items with the same `ParentId` will be rendered at the same level. For a root level item, this must be `null`.
+* `Expanded` - whether the item is expanded when it renders, or the user has to expand it manually.
+* `HasChildren` - whether the item has children. Determines whether an expand arrow is rendered next to the item. Required for binding to flat data and for load-on-demand. With hierarchical data, the treeview will render the icon based on the existence of child items, but `HasChildren` will take precedence.
+* `Items` - the collection of child items that will be rendered under the current item. Required only when binding to hierarchical data.
 * `Text` - the text that will be shown on the item.
 * `Icon` / `IconClass` / `ImageUrl` - the [Telerik icon]({%slug general-information/font-icons%}), a class for a custom font icon, or the URL to a raster image that will be rendered in the item. They have the listed order of precedence in case more than one is present in the data (that is, an `Icon` will have the highest importance).
-* `Expanded` - whether the item is expanded when it renders, or the user has to expand it manually.
-* `HasChildren` - whether the item has children. Determines whether an expand arrow is rendered next to the item. Required.
-* `Items` - the collection of child items that will be rendered under the current item. Needed only when binding to hierarchical data.
 
 ## Data Bindings