Fix Picker ItemDisplayBinding doesn't support MVVM properly

src/Controls/src/Core/Picker/Picker.cs

@@ -264,6 +264,27 @@ static void OnItemsSourceChanged(BindableObject bindable, object oldValue, objec
 
 		void OnItemsSourceChanged(IList oldValue, IList newValue)
 		{
+			if (oldValue is not null)
+			{
+				foreach (var item in oldValue)
+				{
+					if (item is INotifyPropertyChanged npc)
+					{
+						npc.PropertyChanged -= OnPickerItemPropertyChanged;
+					}
+				}
+			}
+			if (newValue is not null && ItemDisplayBinding is not null)
+			{
+				foreach (var item in newValue)
+				{
+					if (item is INotifyPropertyChanged npc)
+					{
+						npc.PropertyChanged += OnPickerItemPropertyChanged;
+					}
+				}
+			}
+
 			var oldObservable = oldValue as INotifyCollectionChanged;
 			if (oldObservable != null)
 				oldObservable.CollectionChanged -= CollectionChanged;
@@ -287,8 +308,40 @@ void OnItemsSourceChanged(IList oldValue, IList newValue)
 			}
 		}
 
+		void OnPickerItemPropertyChanged(object sender, PropertyChangedEventArgs e)
+		{
+			if (ItemDisplayBinding is Binding binding && !string.IsNullOrEmpty(binding.Path))
+			{
+				if (e.PropertyName == binding.Path)
+				{
+					ResetItems();
+				}
+			}
+		}
+
 		void CollectionChanged(object sender, NotifyCollectionChangedEventArgs e)
 		{
+			if (e.OldItems is not null)
+			{
+				foreach (var item in e.OldItems)
+				{
+					if (item is INotifyPropertyChanged npc)
+					{
+						npc.PropertyChanged -= OnPickerItemPropertyChanged;
+					}
+				}
+			}
+			if (e.NewItems is not null && ItemDisplayBinding is not null)
+			{
+				foreach (var item in e.NewItems)
+				{
+					if (item is INotifyPropertyChanged npc)
+					{
+						npc.PropertyChanged += OnPickerItemPropertyChanged;
+					}
+				}
+			}
+
 			switch (e.Action)
 			{
 				case NotifyCollectionChangedAction.Add:

src/Controls/tests/TestCases.HostApp/Issues/Issue25634.cs

@@ -0,0 +1,94 @@
+using System.Collections.ObjectModel;
+using System.ComponentModel;
+using System.Runtime.CompilerServices;
+using Microsoft.Maui.Controls;
+
+namespace Maui.Controls.Sample.Issues;
+
+[Issue(IssueTracker.Github, 25634, "Picker ItemDisplayBinding doesn't support MVVM properly", PlatformAffected.All)]
+public class Issue25634 : ContentPage
+{
+	public ObservableCollection<Issue25634_Model> People { get; private set; } = new()
+	{
+		new Issue25634_Model { FirstName = "John", LastName = "Doe" },
+		new Issue25634_Model { FirstName = "Jane", LastName = "Smith" },
+		new Issue25634_Model { FirstName = "Sam", LastName = "Johnson" }
+	};
+
+	Picker picker;
+
+	public Issue25634()
+	{
+		BindingContext = this;
+
+		picker = new Picker();
+		picker.SetBinding(Picker.ItemsSourceProperty, nameof(People));
+		picker.ItemDisplayBinding = new Binding("LastName");
+
+		var button = new Button 
+		{ 
+			Text = "Click", 
+			AutomationId = "PickerButton" 
+		};
+		button.Clicked += Button_Clicked;
+
+		var stackLayout = new VerticalStackLayout
+		{
+			Padding = new Thickness(30, 0),
+			Spacing = 25
+		};
+		stackLayout.Children.Add(picker);
+		stackLayout.Children.Add(button);
+
+		Content = stackLayout;
+
+		picker.SelectedItem = People[0];
+	}
+
+	void Button_Clicked(object sender, EventArgs e)
+	{
+		if (People.Count > 0)
+		{
+			People[0].LastName = "Alice";
+		}
+	}
+}
+
+public class Issue25634_Model : INotifyPropertyChanged
+{
+	private string firstName = "FirstName";
+	private string lastName = "LastName";
+
+	public string FirstName
+	{
+		get => firstName;
+		set
+		{
+			if (firstName != value)
+			{
+				firstName = value;
+				OnPropertyChanged();
+			}
+		}
+	}
+
+	public string LastName
+	{
+		get => lastName;
+		set
+		{
+			if (lastName != value)
+			{
+				lastName = value;
+				OnPropertyChanged();
+			}
+		}
+	}
+
+	public event PropertyChangedEventHandler PropertyChanged;
+
+	protected void OnPropertyChanged([CallerMemberName] string name = "")
+	{
+		PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(name));
+	}
+}

src/Controls/tests/TestCases.Shared.Tests/Tests/Issues/Issue25634.cs

@@ -0,0 +1,22 @@
+using NUnit.Framework;
+using UITest.Appium;
+using UITest.Core;
+
+namespace Microsoft.Maui.TestCases.Tests.Issues;
+public class Issue25634 : _IssuesUITest
+{
+	public Issue25634(TestDevice testDevice) : base(testDevice)
+	{
+	}
+
+	public override string Issue => "Picker ItemDisplayBinding doesn't support MVVM properly";
+
+	[Test]
+	[Category(UITestCategories.Picker)]
+	public void VerifyPickerItemDisplayBindingValue()
+	{
+		App.WaitForElement("PickerButton");
+		App.Tap("PickerButton");
+		VerifyScreenshot();
+	}
+}