fix(xBind): Add support {x:Null} syntax

src/SourceGenerators/Uno.UI.SourceGenerators/XamlGenerator/XamlFileGenerator.cs

@@ -3664,6 +3664,7 @@ private string BuildXBindEvalFunction(XamlMemberDefinition member, XamlObjectDef
 			rawFunction = rawFunction
 				?.Replace("x:False", "false")
 				.Replace("x:True", "true")
+				.Replace("{x:Null}", "null")
 				.Replace("x:Null", "null")
 				?? "";
 
@@ -3737,6 +3738,7 @@ string buildBindBack()
 			}
 			else
 			{
+				var originalRawFunction = rawFunction;
 				rawFunction = string.IsNullOrEmpty(rawFunction) ? "___ctx" : XBindExpressionParser.Rewrite("___tctx", rawFunction, IsStaticMember);
 
 				string buildBindBack()
@@ -3777,7 +3779,7 @@ string buildBindBack()
 				}
 
 				var bindFunction = $"___ctx is global::{_className.ns + "." + _className.className} ___tctx ? (object)({rawFunction}) : null";
-				return $".Apply(___b =>  /*defaultBindMode{GetDefaultBindMode()}*/ global::Uno.UI.Xaml.BindingHelper.SetBindingXBindProvider(___b, this, ___ctx => {bindFunction}, {buildBindBack()} {pathsArray}))";
+				return $".Apply(___b =>  /*defaultBindMode{GetDefaultBindMode()} {originalRawFunction}*/ global::Uno.UI.Xaml.BindingHelper.SetBindingXBindProvider(___b, this, ___ctx => {bindFunction}, {buildBindBack()} {pathsArray}))";
 			}
 		}
 

src/Uno.UI.Tests/Uno.UI.Tests.csproj

@@ -151,10 +151,6 @@
 		<UpToDateCheckInput Include="**\*.xaml" Exclude="bin\**\*.xaml;obj\**\*.xaml" />
 	</ItemGroup>
 
-	<ItemGroup>
-	  <UpToDateCheckInput Remove="ResourceLoader\Controls\When_Collection_And_InlineProperty.xaml" />
-	</ItemGroup>
-
 	<ItemGroup>
 		<None Update="ResourceLoader\Controls\When_Collection_And_InlineProperty.xaml">
 		  <Generator>MSBuild:Compile</Generator>

src/Uno.UI.Tests/Windows_UI_Xaml_Data/xBindTests/Controls/Binding_xNull.xaml

@@ -0,0 +1,17 @@
+<UserControl
+    x:Class="Uno.UI.Tests.Windows_UI_Xaml_Data.xBindTests.Controls.Binding_xNull"
+    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
+    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
+    xmlns:local="using:Uno.UI.Tests.Windows_UI_Xaml_Data.xBindTests.Controls">
+    <Grid>
+		<TextBlock x:Name="tb01"
+				   x:FieldModifier="public"
+				   Text="{x:Bind Published.ToString('MMM d', {x:Null})}"/>
+		<TextBlock x:Name="tb02"
+				   x:FieldModifier="public"
+				   Text="{x:Bind MyMethod('MMM d', {x:Null})}"/>
+		<TextBlock x:Name="tb03"
+				   x:FieldModifier="public"
+				   Text="{x:Bind MyMethod('MMM d', x:Null)}"/>
+	</Grid>
+</UserControl>

src/Uno.UI.Tests/Windows_UI_Xaml_Data/xBindTests/Controls/Binding_xNull.xaml.cs

@@ -0,0 +1,34 @@
+using System;
+using System.Collections.Generic;
+using System.IO;
+using System.Linq;
+using System.Runtime.InteropServices.WindowsRuntime;
+using Windows.Foundation;
+using Windows.Foundation.Collections;
+using Windows.UI.Xaml;
+using Windows.UI.Xaml.Controls;
+using Windows.UI.Xaml.Controls.Primitives;
+using Windows.UI.Xaml.Data;
+using Windows.UI.Xaml.Input;
+using Windows.UI.Xaml.Media;
+using Windows.UI.Xaml.Navigation;
+
+// The User Control item template is documented at https://go.microsoft.com/fwlink/?LinkId=234236
+
+namespace Uno.UI.Tests.Windows_UI_Xaml_Data.xBindTests.Controls
+{
+	public sealed partial class Binding_xNull : UserControl
+	{
+		public Binding_xNull()
+		{
+			this.InitializeComponent();
+		}
+
+		public DateTime Published => new DateTime(2000, 01, 01);
+
+		public string MyMethod(string myString, object myParam)
+		{
+			return myString + " " + (myParam ?? "<null>");
+		}
+	}
+}

src/Uno.UI.Tests/Windows_UI_Xaml_Data/xBindTests/Given_xBind_Binding.cs

@@ -1069,6 +1069,23 @@ public async Task When_xLoad_Setter_Order()
 			Assert.AreEqual(4, SUT.ellipse.StrokeThickness);
 		}
 
+		[TestMethod]
+		public async Task When_Binding_xNull()
+		{
+			var SUT = new Binding_xNull();
+
+			SUT.ForceLoaded();
+
+			Assert.IsNotNull(SUT.tb01);
+			Assert.AreEqual("Jan 1", SUT.tb01.Text);
+
+			Assert.IsNotNull(SUT.tb02);
+			Assert.AreEqual("MMM d <null>", SUT.tb02.Text);
+
+			Assert.IsNotNull(SUT.tb03);
+			Assert.AreEqual("MMM d <null>", SUT.tb03.Text);
+		}
+
 		private async Task AssertIsNullAsync<T>(Func<T> getter, TimeSpan? timeout = null)
 		{
 			var sw = Stopwatch.StartNew();

src/Uno.UI.Tests/Windows_UI_Xaml_Markup/XamlReaderTests/Given_XamlReader.cs

@@ -733,6 +733,13 @@ public void When_StateTrigger_PropertyPath()
 			var r = Windows.UI.Xaml.Markup.XamlReader.Load(s) as UserControl;
 		}
 
+		[TestMethod]
+		public void When_Brush_And_StringColor()
+		{
+			var s = GetContent(nameof(When_Brush_And_StringColor));
+			var r = Windows.UI.Xaml.Markup.XamlReader.Load(s) as ContentControl;
+		}
+
 		private string GetContent(string testName)
 		{
 			var assembly = this.GetType().Assembly;

src/Uno.UI.Tests/Windows_UI_Xaml_Markup/XamlReaderTests/When_Brush_And_StringColor.xamltest

@@ -0,0 +1,5 @@
+<UserControl xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
+             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
+             x:Name="testPage"
+             Width="42">
+</UserControl>

src/Uno.UI/UI/Xaml/Markup/Reader/XamlObjectBuilder.cs

@@ -103,6 +103,10 @@ private object LoadObject(XamlObjectDefinition control)
 			{
 				return stringValue;
 			}
+			else if (type == typeof(Media.Brush) && control.Members.Where(m => m.Member.Name == "_UnknownContent").FirstOrDefault()?.Value is string brushStringValue)
+			{
+				return XamlBindingHelper.ConvertValue(typeof(Media.Brush), brushStringValue);
+			}
 			else
 			{
 				var instance = Activator.CreateInstance(type);