[C] change searchHandler bindingMode (#5776)

Change the default BindingMode for some properties

- fixes #5706

Xamarin.Forms.Core/SearchHandler.cs

@@ -61,7 +61,7 @@ namespace Xamarin.Forms
 							BindableProperty.Create(nameof(ClearIcon), typeof(ImageSource), typeof(SearchHandler), null, BindingMode.OneTime);
 
 		public static readonly BindableProperty ClearPlaceholderCommandParameterProperty =
-			BindableProperty.Create(nameof(ClearPlaceholderCommandParameter), typeof(object), typeof(SearchHandler), null, BindingMode.OneTime,
+			BindableProperty.Create(nameof(ClearPlaceholderCommandParameter), typeof(object), typeof(SearchHandler), null,
 				propertyChanged: OnClearPlaceholderCommandParameterChanged);
 
 		public static readonly BindableProperty ClearPlaceholderCommandProperty =
@@ -69,7 +69,7 @@ namespace Xamarin.Forms
 				propertyChanged: OnClearPlaceholderCommandChanged);
 
 		public static readonly BindableProperty ClearPlaceholderEnabledProperty =
-			BindableProperty.Create(nameof(ClearPlaceholderEnabled), typeof(bool), typeof(SearchHandler), false, BindingMode.OneWay);
+			BindableProperty.Create(nameof(ClearPlaceholderEnabled), typeof(bool), typeof(SearchHandler), false);
 
 		public static readonly BindableProperty ClearPlaceholderHelpTextProperty =
 			BindableProperty.Create(nameof(ClearPlaceholderHelpText), typeof(string), typeof(SearchHandler), null, BindingMode.OneTime,
@@ -84,7 +84,7 @@ namespace Xamarin.Forms
 				propertyChanged: (b, o, n) => ((SearchHandler)b).UpdateAutomationProperties());
 
 		public static readonly BindableProperty CommandParameterProperty =
-					BindableProperty.Create(nameof(CommandParameter), typeof(object), typeof(SearchHandler), null, BindingMode.OneTime,
+					BindableProperty.Create(nameof(CommandParameter), typeof(object), typeof(SearchHandler), null,
 				propertyChanged: OnCommandParameterChanged);
 
 		public static readonly BindableProperty CommandProperty =

Xamarin.Forms.Xaml.UnitTests/Issues/Gh5706.xaml

@@ -0,0 +1,11 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<Shell  xmlns="http://xamarin.com/schemas/2014/forms"
+        xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
+        x:Class="Xamarin.Forms.Xaml.UnitTests.Gh5706">
+    <Shell.SearchHandler>
+        <SearchHandler
+            x:Name="searchHandler"
+            Command="{Binding FilterCommand}"
+            CommandParameter="{Binding Source={x:Reference searchHandler}, Path=Query}" />
+    </Shell.SearchHandler>
+</Shell>

Xamarin.Forms.Xaml.UnitTests/Issues/Gh5706.xaml.cs

@@ -0,0 +1,60 @@
+using System;
+using System.Collections.Generic;
+using NUnit.Framework;
+using Xamarin.Forms;
+using Xamarin.Forms.Core.UnitTests;
+
+namespace Xamarin.Forms.Xaml.UnitTests
+{
+	public partial class Gh5706 : Shell
+	{
+		class VM
+		{
+			public VM()
+			{
+				FilterCommand = new Command((p) => Param = p);
+			}
+
+			public Command FilterCommand { get; set; }
+
+			public object Param { get; set; }
+		}
+
+		public Gh5706() => InitializeComponent();
+		public Gh5706(bool useCompiledXaml)
+		{
+			//this stub will be replaced at compile time
+		}
+
+		[TestFixture] class Tests
+		{
+			IReadOnlyList<string> _flags;
+
+			[SetUp]
+			public void Setup()
+			{
+				Device.PlatformServices = new MockPlatformServices();
+				_flags = Device.Flags;
+				Device.SetFlags(new List<string>() { ExperimentalFlags.ShellExperimental });
+			}
+
+			[TearDown]
+			public void TearDown()
+			{
+				Device.PlatformServices = null;
+				Device.SetFlags(_flags);
+			}
+
+			[Test]
+			public void ReportSyntaxError([Values(false, true)]bool useCompiledXaml)
+			{
+				var layout = new Gh5706(useCompiledXaml);
+				layout.searchHandler.BindingContext = new VM();
+
+				Assert.That(layout.searchHandler.CommandParameter, Is.Null);
+				layout.searchHandler.Query = "Foo";
+				Assert.That(layout.searchHandler.CommandParameter, Is.EqualTo("Foo"));
+			}
+		}
+	}
+}