Update PageLayout documentation for MenuItemName

docs/en/UI/Blazor/Page-Layout.md

@@ -13,6 +13,37 @@ Title is used to render page title in the PageHeader.
 }
 ```
 
+## MenuItemName
+Indicates current selected menu item name. Menu item name should match a unique menu item name defined using the [Navigation / Menu system](../Blazor/Navigation-Menu.md). In this case, it is expected from the theme to make the menu item "active" in the main menu. 
+
+```csharp
+@inject PageLayout PageLayout
+
+@code {
+    protected override async Task OnInitializedAsync()
+    {
+        PageLayout.MenuItemName = "MyProjectName.Products";
+    }
+}
+```
+
+Menu item name can be set on runtime too.
+
+```html
+@inject PageLayout PageLayout
+
+<Button Clicked="SetCategoriesMenuAsSelected">Change Menu</Button>
+
+@code{
+    protected void SetCategoriesMenuAsSelected()
+    {
+        PageLayout.MenuItemName = "MyProjectName.Categories";
+    }
+}
+```
+
+> Be aware, The [Basic Theme](../Blazor/Basic-Theme.md) currently doesn't support the selected menu item since it is not applicable to the top menu. 
+
 ## BreadCrumbs
 BreadCrumbItems are used to render breadcrumbs in the PageHeader.
 ```csharp