Picker Attribute "SelectedIndex" Not being respected on page load - fix

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

@@ -238,6 +238,9 @@ string GetDisplayMember(object item)
 		static object CoerceSelectedIndex(BindableObject bindable, object value)
 		{
 			var picker = (Picker)bindable;
+			if (picker.Items is not null && !picker._itemsLoaded)
+				return value;
+
 			return picker.Items == null ? -1 : ((int)value).Clamp(-1, picker.Items.Count - 1);
 		}
 
@@ -351,6 +354,7 @@ void ResetItems()
 				((LockableObservableListWrapper)Items).InternalAdd(GetDisplayMember(item));
 			Handler?.UpdateValue(nameof(IPicker.Items));
 
+			_itemsLoaded = true;
 			ClampSelectedIndex();
 		}
 
@@ -434,6 +438,8 @@ void ITextAlignmentElement.OnHorizontalTextAlignmentPropertyChanged(TextAlignmen
 
 		IList<string> IPicker.Items => Items;
 
+		bool _itemsLoaded;
+
 		int IPicker.SelectedIndex
 		{
 			get => SelectedIndex;

src/Controls/tests/TestCases.HostApp/Issues/Issue9150.xaml

@@ -0,0 +1,19 @@
+<?xml version="1.0" encoding="utf-8" ?>
+<ContentPage xmlns="http://schemas.microsoft.com/dotnet/2021/maui"
+             xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
+             x:Class="Maui.Controls.Sample.Issues.Issue9150">
+     <VerticalStackLayout> 
+        <Picker FontSize="15"
+                AutomationId="picker"
+                SelectedIndex="1"
+                x:Name="picker">
+            <Picker.ItemsSource>
+                <x:Array Type="{x:Type x:String}">
+                    <x:String>0</x:String>
+                    <x:String>1</x:String>
+                    <x:String>2</x:String>
+                </x:Array>
+            </Picker.ItemsSource>
+        </Picker>
+    </VerticalStackLayout>
+</ContentPage>

src/Controls/tests/TestCases.HostApp/Issues/Issue9150.xaml.cs

@@ -0,0 +1,15 @@
+using Microsoft.Maui.Controls;
+using Microsoft.Maui.Controls.Xaml;
+
+namespace Maui.Controls.Sample.Issues
+{
+	[XamlCompilation(XamlCompilationOptions.Compile)]
+	[Issue(IssueTracker.Github, 9150, "Picker Attribute \"SelectedIndex\" Not being respected on page load", PlatformAffected.All)]
+	public partial class Issue9150 : ContentPage
+	{
+		public Issue9150()
+		{
+			InitializeComponent();
+		}
+	}
+}

src/Controls/tests/TestCases.Shared.Tests/Tests/Issues/Issue9150.cs

@@ -0,0 +1,25 @@
+using NUnit.Framework;
+using UITest.Appium;
+using UITest.Core;
+
+namespace Microsoft.Maui.TestCases.Tests.Issues
+{
+	public class Issue9150 : _IssuesUITest
+	{
+		public Issue9150(TestDevice device) : base(device)
+		{
+		}
+
+		public override string Issue => "Picker Attribute \"SelectedIndex\" Not being respected on page load";
+
+		[Test]
+		[Category(UITestCategories.Picker)]
+		public void SelectedIndexShouldBeRespectedOnPageLoad()
+		{
+			App.WaitForElement("picker");
+
+			//Selected item should be equal to '1'
+			VerifyScreenshot();
+		}
+	}
+}