added PopToRootAsync method

Source/Xamarin/Prism.Forms.Tests/Navigation/INavigationServiceExtensionsFixture.cs

@@ -0,0 +1,93 @@
+using Prism.Common;
+using Prism.Forms.Tests.Mocks;
+using Prism.Forms.Tests.Mocks.Views;
+using Prism.Navigation;
+using System.Threading.Tasks;
+using Xunit;
+
+namespace Prism.Forms.Tests.Navigation
+{
+    public class INavigationServiceExtensionsFixture
+    {
+        [Fact]
+        public async Task PopToRootAsync_PopsToRoot()
+        {
+            var navigationService = new PageNavigationServiceMock(null, null, null);
+            var rootPage = new Xamarin.Forms.NavigationPage();
+            ((IPageAware)navigationService).Page = rootPage;
+
+            var page1 = new ContentPageMock() { Title = "Page 1" };
+            await rootPage.Navigation.PushAsync(page1);
+
+            await rootPage.Navigation.PushAsync(new ContentPageMock() { Title = "Page 2" });
+            await rootPage.Navigation.PushAsync(new ContentPageMock() { Title = "Page 3" });
+            await rootPage.Navigation.PushAsync(new ContentPageMock() { Title = "Page 4" });
+
+            Assert.True(rootPage.Navigation.NavigationStack.Count == 4);
+
+            await navigationService.PopToRootAsync();
+
+            Assert.Equal(1, rootPage.Navigation.NavigationStack.Count);
+            Assert.Equal(page1, rootPage.Navigation.NavigationStack[0]);
+        }
+
+        [Fact]
+        public async Task PopToRootAsync_PopsToRoot_Destroy()
+        {
+            var recorder = new PageNavigationEventRecorder();
+            var navigationService = new PageNavigationServiceMock(null, null, null);
+            var rootPage = new Xamarin.Forms.NavigationPage();
+            ((IPageAware)navigationService).Page = rootPage;
+
+            var page1 = new ContentPageMock(recorder) { Title = "Page 1" };
+            await rootPage.Navigation.PushAsync(page1);
+
+            var page2 = new ContentPageMock(recorder) { Title = "Page 2" };
+            var page2ViewModel = page2.BindingContext;
+            await rootPage.Navigation.PushAsync(page2);
+
+            var page3 = new ContentPageMock(recorder) { Title = "Page 3" };
+            var page3ViewModel = page3.BindingContext;
+            await rootPage.Navigation.PushAsync(page3);
+
+            var page4 = new ContentPageMock(recorder) { Title = "Page 4" };
+            var page4ViewModel = page4.BindingContext;
+            await rootPage.Navigation.PushAsync(page4);
+
+            Assert.True(rootPage.Navigation.NavigationStack.Count == 4);
+
+            await navigationService.PopToRootAsync();
+
+            Assert.Equal(1, rootPage.Navigation.NavigationStack.Count);
+            Assert.Equal(page1, rootPage.Navigation.NavigationStack[0]);
+            Assert.Equal(6, recorder.Records.Count);
+
+            //page 4
+            var record = recorder.TakeFirst();
+            Assert.Equal(page4, record.Sender);
+            Assert.Equal(PageNavigationEvent.Destroy, record.Event);
+
+            record = recorder.TakeFirst();
+            Assert.Equal(page4ViewModel, record.Sender);
+            Assert.Equal(PageNavigationEvent.Destroy, record.Event);
+
+            //page 3
+            record = recorder.TakeFirst();
+            Assert.Equal(page3, record.Sender);
+            Assert.Equal(PageNavigationEvent.Destroy, record.Event);
+
+            record = recorder.TakeFirst();
+            Assert.Equal(page3ViewModel, record.Sender);
+            Assert.Equal(PageNavigationEvent.Destroy, record.Event);
+
+            //page 2
+            record = recorder.TakeFirst();
+            Assert.Equal(page2, record.Sender);
+            Assert.Equal(PageNavigationEvent.Destroy, record.Event);
+
+            record = recorder.TakeFirst();
+            Assert.Equal(page2ViewModel, record.Sender);
+            Assert.Equal(PageNavigationEvent.Destroy, record.Event);
+        }
+    }
+}

Source/Xamarin/Prism.Forms/Navigation/INavigationServiceExtensions.cs

@@ -0,0 +1,33 @@
+using Prism.Common;
+using System.Collections.Generic;
+using System.Linq;
+using System.Threading.Tasks;
+using Xamarin.Forms;
+
+namespace Prism.Navigation
+{
+    public static class INavigationServiceExtensions
+    {
+        /// <summary>
+        /// When navigating inside a NavigationPage: Pops all but the root Page off the navigation stack
+        /// </summary>
+        /// <param name="navigationService">The INavigatinService instance</param>
+        /// <remarks>Only works when called from a View within a NavigationPage</remarks>
+        public static async Task PopToRootAsync(this INavigationService navigationService)
+        {
+            IPageAware pageAware = (IPageAware)navigationService;
+
+            List<Page> pagesToDestroy = pageAware.Page.Navigation.NavigationStack.ToList(); // get all pages to destroy
+            pagesToDestroy.Reverse(); // destroy them in reverse order
+            pagesToDestroy.Remove(pagesToDestroy.Last()); //don't destroy the root page
+
+            await pageAware.Page.Navigation.PopToRootAsync();
+
+            //BOOM!
+            foreach (var destroyPage in pagesToDestroy)
+            {
+                PageUtilities.DestroyPage(destroyPage);
+            }
+        }
+    }
+}