From 3113198179af4789ea7c02e932f6a17d778169c2 Mon Sep 17 00:00:00 2001
From: Christopher Dresel <christopher.dresel@outlook.com>
Date: Fri, 5 Jul 2019 20:29:42 +0200
Subject: [PATCH] Fix for #6444: Propagate binding context for children of
 shell sections (#6730)

* Propagate binding context for children of shell sections

* Added a few more BindingContext Propagation tests
---
 Xamarin.Forms.Core.UnitTests/ShellTests.cs | 98 ++++++++++++++++++++++++++++++
 Xamarin.Forms.Core/Shell/ShellSection.cs   | 11 +++-
 2 files changed, 108 insertions(+), 1 deletion(-)

diff --git a/Xamarin.Forms.Core.UnitTests/ShellTests.cs b/Xamarin.Forms.Core.UnitTests/ShellTests.cs
index 81c4a25..6ff189d 100644
--- a/Xamarin.Forms.Core.UnitTests/ShellTests.cs
+++ b/Xamarin.Forms.Core.UnitTests/ShellTests.cs
@@ -33,6 +33,104 @@ namespace Xamarin.Forms.Core.UnitTests
 		}
 
 		[Test]
+		public void ShellChildrenBindingContext()
+		{
+			var shell = new Shell();
+
+			var shellItem = CreateShellItem();
+			shell.Items.Add(shellItem);
+
+			object viewModel = new object();
+			shell.BindingContext = viewModel;
+
+			Assert.AreSame(shell.BindingContext, viewModel);
+			Assert.AreSame(shellItem.BindingContext, viewModel);
+			Assert.AreSame(shellItem.Items[0].BindingContext, viewModel);
+			Assert.AreSame(shellItem.Items[0].Items[0].BindingContext, viewModel);
+			Assert.AreSame((shellItem.Items[0].Items[0].Content as BindableObject).BindingContext, viewModel);
+		}
+
+		[Test]
+		public void ShellPropagateBindingContextWhenAddingNewShellItem()
+		{
+			var shell = new Shell();
+
+			shell.Items.Add(CreateShellItem());
+
+			object viewModel = new object();
+			shell.BindingContext = viewModel;
+			var shellItem = CreateShellItem();
+			shell.Items.Add(shellItem);
+
+			Assert.AreSame(shellItem.BindingContext, viewModel);
+			Assert.AreSame(shellItem.Items[0].BindingContext, viewModel);
+			Assert.AreSame(shellItem.Items[0].Items[0].BindingContext, viewModel);
+			Assert.AreSame((shellItem.Items[0].Items[0].Content as BindableObject).BindingContext, viewModel);
+		}
+
+		[Test]
+		public void ShellPropagateBindingContextWhenAddingNewShellSection()
+		{
+			var shell = new Shell();
+
+			shell.Items.Add(CreateShellItem());
+
+			object viewModel = new object();
+			shell.BindingContext = viewModel;
+			var shellSection = CreateShellSection();
+			shell.Items[0].Items.Add(shellSection);
+
+			Assert.AreSame(shellSection.BindingContext, viewModel);
+			Assert.AreSame(shellSection.Items[0].BindingContext, viewModel);
+			Assert.AreSame((shellSection.Items[0].Content as BindableObject).BindingContext, viewModel);
+		}
+
+		[Test]
+		public void ShellPropagateBindingContextWhenAddingNewShellContent()
+		{
+			var shell = new Shell();
+
+			shell.Items.Add(CreateShellItem());
+
+			object viewModel = new object();
+			shell.BindingContext = viewModel;
+			var shellContent = CreateShellContent();
+			shell.Items[0].Items[0].Items.Add(shellContent);
+
+			Assert.AreSame(shellContent.BindingContext, viewModel);
+			Assert.AreSame((shellContent.Content as BindableObject).BindingContext, viewModel);
+		}
+
+		[Test]
+		public void ShellPropagateBindingContextWhenChangingContent()
+		{
+			var shell = new Shell();
+
+			shell.Items.Add(CreateShellItem());
+
+			object viewModel = new object();
+			shell.BindingContext = viewModel;
+			var contentPage = new ContentPage();
+
+			shell.Items[0].Items[0].Items[0].Content = contentPage;
+			Assert.AreSame(contentPage.BindingContext, viewModel);
+		}
+
+		[Test]
+		public async Task ShellPropagateBindingContextWhenPushingContent()
+		{
+			var shell = new Shell();
+			shell.Items.Add(CreateShellItem());
+
+			object viewModel = new object();
+			shell.BindingContext = viewModel;
+			var contentPage = new ContentPage();
+			await shell.Navigation.PushAsync(contentPage);
+
+			Assert.AreSame(contentPage.BindingContext, viewModel);
+		}
+
+		[Test]
 		public void NavigationProxyWireUpTest()
 		{
 			var page = new ContentPage();
diff --git a/Xamarin.Forms.Core/Shell/ShellSection.cs b/Xamarin.Forms.Core/Shell/ShellSection.cs
index fdc4a2d..d3c5027 100644
--- a/Xamarin.Forms.Core/Shell/ShellSection.cs
+++ b/Xamarin.Forms.Core/Shell/ShellSection.cs
@@ -598,11 +598,20 @@ namespace Xamarin.Forms
 			}
 		}
 
+		protected override void OnBindingContextChanged()
+		{
+			base.OnBindingContextChanged();
+
+			foreach (ShellContent shellContent in Items)
+			{
+				SetInheritedBindingContext(shellContent, BindingContext);
+			}
+		}
+    
 		internal override void SendDisappearing()
 		{
 			base.SendDisappearing();
 			PresentedPageDisappearing();
-
 		}
 
 		internal override void SendAppearing()
-- 
2.7.4