Created Sample for Picker dialog customization

10.0/UserInterface/PickerDemo/App.xaml

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+<?xml version="1.0" encoding="UTF-8" ?>
+<Application xmlns="http://schemas.microsoft.com/dotnet/2021/maui"
+             xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
+             xmlns:local="clr-namespace:PickerDemo"
+             x:Class="PickerDemo.App">
+    <Application.Resources>
+        <ResourceDictionary>
+            <ResourceDictionary.MergedDictionaries>
+                <ResourceDictionary Source="Resources/Styles/Colors.xaml"/>
+                <ResourceDictionary Source="Resources/Styles/Styles.xaml"/>
+                <ResourceDictionary Source="Resources/Styles/AppStyles.xaml"/>
+            </ResourceDictionary.MergedDictionaries>
+        </ResourceDictionary>
+    </Application.Resources>
+</Application>

10.0/UserInterface/PickerDemo/App.xaml.cs

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+namespace PickerDemo;
+
+public partial class App : Application
+{
+    public App()
+    {
+        InitializeComponent();
+    }
+
+    protected override Window CreateWindow(IActivationState? activationState)
+    {
+        return new Window(new AppShell());
+    }
+}

10.0/UserInterface/PickerDemo/AppShell.xaml

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+<?xml version="1.0" encoding="UTF-8" ?>
+<Shell
+    x:Class="PickerDemo.AppShell"
+    xmlns="http://schemas.microsoft.com/dotnet/2021/maui"
+    xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
+    xmlns:local="clr-namespace:PickerDemo"
+    Title="PickerDemo">
+
+    <ShellContent
+        Title="Home"
+        ContentTemplate="{DataTemplate local:MainPage}"
+        Route="MainPage"/>
+
+</Shell>

10.0/UserInterface/PickerDemo/AppShell.xaml.cs

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+namespace PickerDemo;
+
+public partial class AppShell : Shell
+{
+    public AppShell()
+    {
+        InitializeComponent();
+    }
+}

10.0/UserInterface/PickerDemo/Control/CustomPicker.cs

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+using Microsoft.Maui.Platform;
+
+namespace PickerDemo.Control;
+
+public class CustomPicker : Picker, ICustomPicker
+{
+    public static readonly BindableProperty DialogBackgroundColorProperty =
+  BindableProperty.Create(nameof(DialogBackgroundColor), typeof(Color), typeof(CustomPicker), null);
+
+    public static readonly BindableProperty DialogTextColorProperty =
+        BindableProperty.Create(nameof(DialogTextColor), typeof(Color), typeof(CustomPicker), null);
+
+    public static readonly BindableProperty SelectedTextColorProperty =
+            BindableProperty.Create(nameof(SelectedTextColor), typeof(Color), typeof(CustomPicker), null);
+
+    public Color SelectedTextColor
+    {
+        get => (Color)GetValue(SelectedTextColorProperty);
+        set => SetValue(SelectedTextColorProperty, value);
+    }
+
+    public Color DialogBackgroundColor
+    {
+        get => (Color)GetValue(DialogBackgroundColorProperty);
+        set => SetValue(DialogBackgroundColorProperty, value);
+    }
+
+    public Color DialogTextColor
+    {
+        get => (Color)GetValue(DialogTextColorProperty);
+        set => SetValue(DialogTextColorProperty, value);
+    }
+}

10.0/UserInterface/PickerDemo/Control/ICustomPicker.cs

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+namespace PickerDemo.Control;
+
+public interface ICustomPicker
+{
+    Color DialogBackgroundColor { get; }
+    Color DialogTextColor { get; }
+    Color SelectedTextColor { get; }
+}

10.0/UserInterface/PickerDemo/GlobalUsings.cs

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+global using System.Collections.ObjectModel;
+global using System.ComponentModel;
+global using Microsoft.Extensions.Logging;

10.0/UserInterface/PickerDemo/Handlers/CustomPickerHandler.Android.cs

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+using System.Reflection;
+using Microsoft.Maui.Handlers;
+using Android.Widget;
+using AppCompatAlertDialog = AndroidX.AppCompat.App.AlertDialog;
+using MauiPicker = Microsoft.Maui.Platform.MauiPicker;
+using PickerDemo.Control;
+using Microsoft.Maui.Platform;
+using AndroidView = Android.Views.View;
+using AndroidViewGroup = Android.Views.ViewGroup;
+
+namespace PickerDemo.Handlers;
+
+public partial class CustomPickerHandler : PickerHandler
+{
+    // TODO: To avoid using reflection code, the _dialog variable should be exposed as protected in the PickerHandler.Android. 
+    private FieldInfo? _dialogFieldInfo;
+
+    protected override void ConnectHandler(MauiPicker platformView)
+    {
+        base.ConnectHandler(platformView);
+
+        // Cache the FieldInfo (only done once)
+        _dialogFieldInfo ??= GetDialogField();
+
+        platformView.Click += OnCustomizeDialog;
+    }
+
+    // TODO: To avoid using reflection code, the _dialog variable should be exposed as protected in the PickerHandler.Android.
+    static FieldInfo? GetDialogField()
+    {
+        return typeof(PickerHandler).GetField("_dialog",
+            BindingFlags.NonPublic |
+            BindingFlags.Instance);
+    }
+
+    protected override void DisconnectHandler(MauiPicker platformView)
+    {
+        platformView.Click -= OnCustomizeDialog;
+        base.DisconnectHandler(platformView);
+    }
+
+    void OnCustomizeDialog(object? sender, EventArgs e)
+    {
+        if (VirtualView is not CustomPicker customPicker)
+        {
+            return;
+        }
+
+        // Get dialog via reflection (unavoidable without framework changes)
+        var dialog = _dialogFieldInfo?.GetValue(this) as AppCompatAlertDialog;
+
+        // Apply background color to the dialog window
+        if (dialog?.Window is not null && customPicker.DialogBackgroundColor is not null)
+        {
+            dialog.Window.SetBackgroundDrawable(new Android.Graphics.Drawables.ColorDrawable(customPicker.DialogBackgroundColor.ToPlatform()));
+        }
+
+        var dialogListView = dialog?.ListView;
+        if (dialogListView?.Adapter is not null)
+        {
+            // Wrap the original adapter with custom adapter
+            var customAdapter = new ColoredPickerAdapter(
+                dialogListView.Adapter,
+                customPicker.DialogTextColor,
+                customPicker.SelectedTextColor,
+                VirtualView?.SelectedIndex ?? -1);
+
+            // Set the custom adapter - this ensures GetView() is called for each item
+            dialogListView.Adapter = customAdapter;
+            if (VirtualView?.SelectedIndex >= 0)
+            {
+                dialogListView.SetItemChecked(VirtualView.SelectedIndex, true);
+            }
+        }
+    }
+}
+
+/// <summary>
+/// Custom adapter that wraps the original picker adapter and applies custom text colors.
+/// This ensures colors are applied during view creation.
+/// </summary>
+internal class ColoredPickerAdapter : BaseAdapter
+{
+    private readonly IListAdapter _baseAdapter;
+    private readonly Color? _textColor;
+    private readonly Color? _selectedTextColor;
+    private readonly int _selectedPosition;
+
+    public ColoredPickerAdapter(
+        IListAdapter baseAdapter,
+        Color? textColor,
+        Color? selectedTextColor,
+        int selectedPosition)
+    {
+        _baseAdapter = baseAdapter ?? throw new ArgumentNullException(nameof(baseAdapter));
+        _textColor = textColor;
+        _selectedTextColor = selectedTextColor;
+        _selectedPosition = selectedPosition;
+    }
+
+    // Return the total number of items from the original adapter
+    public override int Count => _baseAdapter.Count;
+
+    // Return the data item at the specified position
+    public override Java.Lang.Object? GetItem(int position) => _baseAdapter.GetItem(position);
+
+    // Return the unique identifier for the item at the specified position
+    public override long GetItemId(int position) => _baseAdapter.GetItemId(position);
+
+    public override AndroidView? GetView(int position, AndroidView? convertView, AndroidViewGroup? parent)
+    {
+        // Get the view from the original adapter.
+        var view = _baseAdapter.GetView(position, convertView, parent);
+
+        // Customize the view if it's a CheckedTextView
+        if (view is CheckedTextView textView)
+        {
+            var isSelected = position == _selectedPosition;
+
+            // Apply the appropriate text color based on selection state
+            var color = isSelected ? _selectedTextColor : _textColor;
+            if (color is not null)
+            {
+                textView.SetTextColor(color.ToPlatform());
+            }
+        }
+
+        return view;
+    }
+}

10.0/UserInterface/PickerDemo/Handlers/CustomPickerHandler.Windows.cs

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+using Microsoft.Maui.Handlers;
+using Microsoft.UI.Xaml.Controls;
+using WinColor = Windows.UI.Color;
+using PickerDemo.Control;
+using MauiColor = Microsoft.Maui.Graphics.Color;
+using SolidColorBrush = Microsoft.UI.Xaml.Media.SolidColorBrush;
+
+namespace PickerDemo.Handlers;
+
+public partial class CustomPickerHandler : PickerHandler
+{
+    protected override ComboBox CreatePlatformView()
+    {
+        var comboBox = base.CreatePlatformView();
+        if (VirtualView is CustomPicker customPicker)
+        {
+            UpdateComboBoxStyle(comboBox, customPicker);
+        }
+        return comboBox;
+    }
+
+    public static void MapDialogBackgroundColor(CustomPickerHandler handler, CustomPicker picker)
+    {
+        if (handler.PlatformView is ComboBox comboBox)
+        {
+            UpdateComboBoxStyle(comboBox, picker);
+        }
+    }
+
+    public static void MapDialogTextColor(CustomPickerHandler handler, CustomPicker picker)
+    {
+        if (handler.PlatformView is ComboBox comboBox)
+        {
+            UpdateComboBoxStyle(comboBox, picker);
+        }
+    }
+
+    public static void MapSelectedTextColor(CustomPickerHandler handler, CustomPicker picker)
+    {
+        if (handler.PlatformView is ComboBox comboBox)
+        {
+            UpdateComboBoxStyle(comboBox, picker);
+        }
+    }
+
+    static void UpdateComboBoxStyle(ComboBox comboBox, CustomPicker picker)
+    {
+        // Apply same colors to dropdown items
+        var itemStyle = new Microsoft.UI.Xaml.Style(typeof(ComboBoxItem));
+
+        // Apply dialog background color if provided
+        if (picker.DialogBackgroundColor is not null)
+        {
+            var dialogBackgroundColor = ConvertToWinColor(picker.DialogBackgroundColor);
+            itemStyle.Setters.Add(new Microsoft.UI.Xaml.Setter(ComboBoxItem.BackgroundProperty, new SolidColorBrush(dialogBackgroundColor)));
+        }
+
+        // Apply dialog text color if provided
+        if (picker.DialogTextColor is not null)
+        {
+            var textColor = ConvertToWinColor(picker.DialogTextColor);
+            itemStyle.Setters.Add(new Microsoft.UI.Xaml.Setter(ComboBoxItem.ForegroundProperty, new SolidColorBrush(textColor)));
+        }
+
+        // Apply selected text color if provided
+        if (picker.SelectedTextColor is not null)
+        {
+            var selectedTextColor = ConvertToWinColor(picker.SelectedTextColor);
+            var selectedForegroundBrush = new SolidColorBrush(selectedTextColor);
+            // Add custom resources that will be used for selected state
+            comboBox.Resources["ComboBoxItemForegroundSelected"] = selectedForegroundBrush;
+        }
+
+        comboBox.Resources[typeof(ComboBoxItem)] = itemStyle;
+    }
+
+    static WinColor ConvertToWinColor(MauiColor color)
+    {
+        return WinColor.FromArgb(
+   (byte)(color.Alpha * 255),
+      (byte)(color.Red * 255),
+            (byte)(color.Green * 255),
+    (byte)(color.Blue * 255)
+);
+    }
+}

10.0/UserInterface/PickerDemo/Handlers/CustomPickerHandler.cs

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+using Microsoft.Maui.Handlers;
+using PickerDemo.Control;
+using Microsoft.Maui;
+
+namespace PickerDemo.Handlers;
+
+public partial class CustomPickerHandler : PickerHandler, IElementHandler
+{
+    public static IPropertyMapper<CustomPicker, CustomPickerHandler> CustomMapper { get; } =
+        new PropertyMapper<CustomPicker, CustomPickerHandler>(PickerHandler.Mapper)
+        {
+#if IOS || WINDOWS
+            [nameof(CustomPicker.DialogBackgroundColor)] = MapDialogBackgroundColor,
+            [nameof(CustomPicker.DialogTextColor)] = MapDialogTextColor,
+            [nameof(CustomPicker.SelectedTextColor)] = MapSelectedTextColor
+#endif
+        };
+
+    public CustomPickerHandler() : base(CustomMapper)
+    {
+    }
+
+    public CustomPickerHandler(IPropertyMapper? mapper = null)
+        : base(mapper ?? CustomMapper)
+    {
+    }
+}