From: Stephane Delcroix <stephane@delcroix.org>
Date: Thu, 14 Feb 2019 19:08:16 +0000 (+0100)
Subject: [C] Binding null on nullable (#5255)
X-Git-Tag: accepted/tizen/5.5/unified/20200421.150457~500^2
X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=748da1e628900efe2309cb5d4bd796c4f1eb30cd;p=platform%2Fcore%2Fcsapi%2Fxsf.git

[C] Binding null on nullable (#5255)

* fixes pull #4453

bindings should allow null for nullable valuetypes!

* [C] Binding null on nullable

@kicsiede's fix for #5242, plus unit test, targetted to 3.6.0

- closes #5242
---

diff --git a/Xamarin.Forms.Core/BindingExpression.cs b/Xamarin.Forms.Core/BindingExpression.cs
index 163b369..903d391 100644
--- a/Xamarin.Forms.Core/BindingExpression.cs
+++ b/Xamarin.Forms.Core/BindingExpression.cs
@@ -1,4 +1,4 @@
-using System;
+using System;
 using System.Collections.Generic;
 using System.ComponentModel;
 using System.Diagnostics;
@@ -429,7 +429,7 @@ namespace Xamarin.Forms
 		internal static bool TryConvert(ref object value, BindableProperty targetProperty, Type convertTo, bool toTarget)
 		{
 			if (value == null)
-				return !convertTo.GetTypeInfo().IsValueType;
+				return !convertTo.GetTypeInfo().IsValueType || Nullable.GetUnderlyingType(convertTo) != null;
 			if ((toTarget && targetProperty.TryConvert(ref value)) || (!toTarget && convertTo.IsInstanceOfType(value)))
 				return true;
 
diff --git a/Xamarin.Forms.Xaml.UnitTests/Issues/Gh5242.xaml b/Xamarin.Forms.Xaml.UnitTests/Issues/Gh5242.xaml
new file mode 100644
index 0000000..aba2aa3
--- /dev/null
+++ b/Xamarin.Forms.Xaml.UnitTests/Issues/Gh5242.xaml
@@ -0,0 +1,8 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<ContentPage
+        xmlns="http://xamarin.com/schemas/2014/forms"
+        xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
+        xmlns:local="using:Xamarin.Forms.Xaml.UnitTests"
+        x:Class="Xamarin.Forms.Xaml.UnitTests.Gh5242"
+        NullableInt="{Binding Value}" x:DataType="local:Gh5242VM">
+</ContentPage>
diff --git a/Xamarin.Forms.Xaml.UnitTests/Issues/Gh5242.xaml.cs b/Xamarin.Forms.Xaml.UnitTests/Issues/Gh5242.xaml.cs
new file mode 100644
index 0000000..130ac4d
--- /dev/null
+++ b/Xamarin.Forms.Xaml.UnitTests/Issues/Gh5242.xaml.cs
@@ -0,0 +1,45 @@
+using System;
+using System.Collections.Generic;
+
+using NUnit.Framework;
+
+using Xamarin.Forms;
+using Xamarin.Forms.Core.UnitTests;
+
+namespace Xamarin.Forms.Xaml.UnitTests
+{
+	public class Gh5242VM
+	{
+		public int? Value {get;set;}
+	}
+
+	public partial class Gh5242 : ContentPage
+	{
+		public static readonly BindableProperty NullableIntProperty = BindableProperty.Create("NullableInt", typeof(int?), typeof(Gh5242), defaultValue:-1);
+		public int? NullableInt { get => (int?)GetValue(NullableIntProperty); }
+
+		public Gh5242() => InitializeComponent();
+		public Gh5242(bool useCompiledXaml)
+		{
+			//this stub will be replaced at compile time
+		}
+
+		[TestFixture]
+		class Tests
+		{
+			[SetUp] public void Setup() => Device.PlatformServices = new MockPlatformServices();
+			[TearDown] public void TearDown() => Device.PlatformServices = null;
+
+			[Test]
+			public void BindingToNullable([Values (false, true)]bool useCompiledXaml)
+			{
+				var layout = new Gh5242(useCompiledXaml) {BindingContext = new Gh5242VM {Value = 42}};
+				Assert.That(layout.NullableInt, Is.EqualTo(42));
+
+				layout.BindingContext = new Gh5242VM { Value = null };
+				Assert.That(layout.NullableInt, Is.Null);
+			}
+		}
+
+	}
+}