Demo: Process change events in PropertyGrid (#512)

Author: axunonb

src/Demo/Sample Extensions/ItemCollectionWrapper.cs

@@ -0,0 +1,37 @@
+//
+// Copyright SmartFormat Project maintainers and contributors.
+// Licensed under the MIT license.
+//
+
+using System.Collections.Generic;
+using System.ComponentModel;
+
+namespace Demo.Sample_Extensions;
+
+public class InventoryItem {
+    public string Name { get; set; } = string.Empty;
+    public decimal Price { get; set; }
+    public int Count { get; set; }
+    public List<InventoryItem> Components { get; set; } = [];
+    public override string ToString() => $"{Name} (Comp: {Components.Count})";
+}
+
+public class ItemCollectionWrapper
+{
+    // Use the ExpandableObjectConverter so the PropertyGrid
+    // shows a '+' sign next to the property to expand it.
+    [TypeConverter(typeof(ExpandableObjectConverter))]
+    // Use the Category and Description attributes for better display in the grid
+    [Category("Products")]
+    [DisplayName("Items")]
+    [Browsable(true)]
+    public List<InventoryItem> Items { get; set; }
+
+    public ItemCollectionWrapper(List<InventoryItem> items)
+    {
+        Items = items;
+    }
+
+    public override string ToString() => $"{Items.Count} items";
+
+}