[WPF] Fixed the NRE in FormWindow (#11926) fixes #11923

Author: jsuarezruiz

Xamarin.Forms.ControlGallery.WPF/Issue11923.cs

@@ -0,0 +1,51 @@
+using System;
+using System.Threading;
+using System.Threading.Tasks;
+using System.Windows;
+using Xamarin.Forms.Controls.Issues;
+using Xamarin.Forms.Platform.WPF;
+
+namespace Xamarin.Forms.ControlGallery.WPF
+{
+	// To test this issue modify the csproj to modify the Application entry point.
+	// <StartupObject>Xamarin.Forms.ControlGallery.WPF.Issue11923</StartupObject>
+	// And uncomment the static Main method.
+	class Issue11923
+	{
+		/*
+		[STAThread]
+		static void Main(string[] args)
+		{
+			var application = new System.Windows.Application();
+			Forms.SetFlags("CarouselView_Experimental", "MediaElement_Experimental", "RadioButton_Experimental");
+			FormsMaps.Init("");
+			Forms.Init();
+			var formsApplicationPage = new FormsApplicationPage();
+			formsApplicationPage.LoadApplication(new Controls.App());
+
+			Task.Run(() =>
+			{
+				Task.Delay(1000).Wait();
+
+				application.Dispatcher.InvokeAsync(() =>
+				{
+					var window = new Window()
+					{
+						Height = 600,
+						Width = 600
+					};
+
+					var mainPage = new Issue1();
+					var formsContentLoader = new FormsContentLoader();
+					var content = formsContentLoader.LoadContentAsync(window, null, mainPage, new CancellationToken()).Result;
+
+					window.Content = content;
+					window.Show();
+				});
+			});
+
+			application.Run();
+		}
+		*/
+	}
+}

Xamarin.Forms.ControlGallery.WPF/Xamarin.Forms.ControlGallery.WPF.csproj

@@ -1,4 +1,4 @@
-<Project Sdk="Microsoft.NET.Sdk.WindowsDesktop">
+<Project Sdk="Microsoft.NET.Sdk.WindowsDesktop">
   <PropertyGroup>
     <TargetFrameworks Condition=" '$(OS)' == 'Windows_NT' ">netcoreapp3.1;net461;</TargetFrameworks>
     <TargetFrameworks Condition=" '$(OS)' != 'Windows_NT' ">net461;</TargetFrameworks>
@@ -7,8 +7,8 @@
     <OutputType>WinExe</OutputType>
     <UseWPF>true</UseWPF>
     <AppendTargetFrameworkToOutputPath>true</AppendTargetFrameworkToOutputPath>
-    <GenerateAssemblyInfo>false</GenerateAssemblyInfo>    
-    <AutoGenerateBindingRedirects>true</AutoGenerateBindingRedirects>
+    <GenerateAssemblyInfo>true</GenerateAssemblyInfo>    
+    <AutoGenerateBindingRedirects>true</AutoGenerateBindingRedirects>  
   </PropertyGroup>
   <PropertyGroup>
     <NoWarn>$(NoWarn);NU1701</NoWarn>

Xamarin.Forms.Platform.WPF/Controls/FormWindow.cs

@@ -199,7 +199,8 @@ public void SynchronizeAppBar()
 				ClearValue(TitleBarTextColorProperty);
 			}
 
-			hamburgerButton.Visibility = CurrentMasterDetailPage != null ? Visibility.Visible : Visibility.Collapsed;
+			if (hamburgerButton != null)
+				hamburgerButton.Visibility = CurrentMasterDetailPage != null ? Visibility.Visible : Visibility.Collapsed;
 
 			if (CurrentNavigationPage != null)
 			{

Xamarin.Forms.Platform.WPF/Properties/AssemblyInfo.cs

@@ -1,4 +1,5 @@
-using System.Windows;
+using System.Reflection;
+using System.Windows;
 using Xamarin.Forms;
 using Xamarin.Forms.Platform.WPF;
 using Xamarin.Forms.Shapes;
@@ -71,4 +72,6 @@
 
 // Others
 [assembly: Xamarin.Forms.Dependency(typeof(ResourcesProvider))]
-[assembly: Xamarin.Forms.Dependency(typeof(Deserializer))]
+[assembly: Xamarin.Forms.Dependency(typeof(Deserializer))]
+
+[assembly: AssemblyVersion("2.0.0.0")]