Fix for Windows SearchBar MaxLength > 0 not working properly.

src/Controls/tests/TestCases.HostApp/Issues/Issue5669.xaml

@@ -0,0 +1,15 @@
+<?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.Issue5669">
+  <ContentPage.Content>
+    <StackLayout>
+      <SearchBar x:Name="searchbar" Text="Searchbar Control" MaxLength="3" AutomationId="SearchBar"/>
+      <HorizontalStackLayout>
+        <Label Text="MaxLength value is: "/>
+        <Label Text="{Binding Source={x:Reference searchbar}, Path=MaxLength}"/>
+      </HorizontalStackLayout>
+      <Button AutomationId="ChangeValue" Text="Change Value" x:Name="button" Clicked="Button_Clicked"/>
+    </StackLayout>
+  </ContentPage.Content>
+</ContentPage>

src/Controls/tests/TestCases.HostApp/Issues/Issue5669.xaml.cs

@@ -0,0 +1,17 @@
+namespace Maui.Controls.Sample.Issues
+{ 
+	[XamlCompilation(XamlCompilationOptions.Compile)]
+	[Issue(IssueTracker.Github, 5669, "Windows SearchBar MaxLength > 0 not working properly", PlatformAffected.UWP)]
+	public partial class Issue5669 : ContentPage
+	{
+		public Issue5669()
+		{
+			InitializeComponent();
+		}
+
+		private void Button_Clicked(object sender, EventArgs e)
+		{
+			searchbar.MaxLength = 4;
+		}
+    }
+}

src/Controls/tests/TestCases.Shared.Tests/Tests/Issues/Issue5669.cs

@@ -0,0 +1,28 @@
+#if !MACCATALYST
+using NUnit.Framework;
+using UITest.Appium;
+using UITest.Core;
+
+namespace Microsoft.Maui.TestCases.Tests.Issues
+{
+    public class Issue5669: _IssuesUITest
+	{
+		public override string Issue => "Windows SearchBar MaxLength > 0 not working properly";
+		public Issue5669(TestDevice testDevice) : base(testDevice)
+		{
+		}
+
+		[Test]
+		[Category(UITestCategories.SearchBar)]
+		public void SearchBarMaxLength() 
+		{
+			App.WaitForElement("SearchBar");
+			App.EnterText("SearchBar", "r");
+			App.Click("ChangeValue");
+			App.EnterText("SearchBar", "r");
+			App.EnterText("SearchBar", "c");
+			VerifyScreenshot();
+		}
+	}
+}
+#endif

src/Core/src/Platform/Windows/SearchBarExtensions.cs

@@ -112,6 +112,19 @@ public static void UpdateMaxLength(this AutoSuggestBox platformControl, ISearchB
 			if (maxLength == -1)
 				maxLength = int.MaxValue;
 
+			var children = platformControl.GetChildren<TextBox>();
+			if (children is not null)
+			{
+				foreach (var textBox in children)
+				{
+					if (textBox is not null)
+					{
+						textBox.MaxLength = searchBar.MaxLength;
+						break;
+					}
+				}
+			}
+
 			if (maxLength == 0)
 				MauiAutoSuggestBox.SetIsReadOnly(platformControl, true);
 			else