adding SelectTabExtension

Sandbox/Xamarin/HelloWorld/ModuleA/Views/ViewA.xaml

@@ -1,7 +1,7 @@
 <?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:prism="clr-namespace:Prism.Mvvm;assembly=Prism.Forms"
+             xmlns:prism="http://prismlibrary.com"
              prism:ViewModelLocator.AutowireViewModel="True"
              x:Class="ModuleA.Views.ViewA"
              Padding="{OnPlatform iOS='0,20,0,0'}"
@@ -23,6 +23,8 @@
         <Label Text="{Binding Message}" />
         <Label Text="{Binding IsActive, StringFormat='IsActive: {0}'}" />
         <Button Command="{Binding NavigateCommand}" Text="Navigate" />
+        <Button Text="Select Tab C"
+                Command="{prism:SelectTab ViewC}" />
     </StackLayout>
 
 </ContentPage>

Sandbox/Xamarin/HelloWorld/ModuleA/Views/ViewB.xaml

@@ -2,22 +2,20 @@
 <ContentPage xmlns="http://xamarin.com/schemas/2014/forms"
              xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
              xmlns:local="clr-namespace:ModuleA.Views"
-             xmlns:prism="clr-namespace:Prism.Mvvm;assembly=Prism.Forms"
+             xmlns:prism="http://prismlibrary.com"
              prism:ViewModelLocator.AutowireViewModel="True"
              x:Class="ModuleA.Views.ViewB"
              x:Name="viewB"
+             Padding="{OnPlatform iOS='0,20,0,0'}"
              Title="View B">
-    <ContentPage.Padding>
-        <OnPlatform x:TypeArguments="Thickness">
-            <On Platform="iOS" Value="0,20,0,0" />
-        </OnPlatform>
-    </ContentPage.Padding>
 
     <!--<local:PartialViewB prism:ViewModelLocator.AutowirePartialView="{x:Reference viewB}" />-->
     <StackLayout>
         <Label Text="{Binding Title}" VerticalOptions="Center" HorizontalOptions="Center" />
         <Label Text="{Binding IsActive}" />
         <Button Command="{Binding NavigateCommand}" Text="Navigate" />
+        <Button Text="Select Tab C"
+                Command="{prism:SelectTab ViewC}" />
     </StackLayout>
 
 </ContentPage>

Sandbox/Xamarin/HelloWorld/ModuleA/Views/ViewC.xaml

@@ -1,17 +1,15 @@
 <?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:prism="clr-namespace:Prism.Mvvm;assembly=Prism.Forms"
+             xmlns:prism="http://prismlibrary.com"
              prism:ViewModelLocator.AutowireViewModel="True"
              x:Class="ModuleA.Views.ViewC"
+             Padding="{OnPlatform iOS='0,20,0,0'}"
              Title="View C">
-    <ContentPage.Padding>
-        <OnPlatform x:TypeArguments="Thickness">
-            <On Platform="iOS" Value="0,20,0,0" />
-        </OnPlatform>
-    </ContentPage.Padding>
   <StackLayout>
     <Label Text="{Binding Title}" VerticalOptions="Center" HorizontalOptions="Center" />
     <Button Command="{Binding NavigateCommand}" Text="Navigate" />
   </StackLayout>
+        <Button Text="Select Tab A"
+                Command="{prism:SelectTab ViewA}" />
 </ContentPage>

Source/Xamarin/Prism.Forms/Navigation/Xaml/NavigationExtensionBase.cs

@@ -14,7 +14,7 @@ public abstract class NavigationExtensionBase : Prism.Xaml.ParentPageAwareExtens
         public static readonly BindableProperty UseModalNavigationProperty =
             BindableProperty.Create(nameof(UseModalNavigation), typeof(bool?), typeof(NavigationExtensionBase), null);
 
-        protected internal bool IsNavigating;
+        protected internal bool IsNavigating { get; private set; }
 
         public bool Animated
         {

Source/Xamarin/Prism.Forms/Navigation/Xaml/SelectTabExtension.cs

@@ -0,0 +1,73 @@
+using System;
+using System.Collections.Generic;
+using System.Text;
+using System.Threading.Tasks;
+using System.Windows.Input;
+using Prism.Navigation.TabbedPages;
+using Prism.Xaml;
+using Xamarin.Forms;
+
+namespace Prism.Navigation.Xaml
+{
+    [ContentProperty(nameof(Name))]
+    public class SelectTabExtension : ParentPageAwareExtension<ICommand>, ICommand
+    {
+        public static readonly BindableProperty NameProperty =
+               BindableProperty.Create(nameof(Name), typeof(string), typeof(NavigateToExtension), null);
+
+        public string Name
+        {
+            get => (string)GetValue(NameProperty);
+            set => SetValue(NameProperty, value);
+        }
+
+        protected internal bool IsNavigating { get; private set; }
+
+        public event EventHandler CanExecuteChanged;
+
+        public bool CanExecute(object parameter) => !IsNavigating;
+
+        public async void Execute(object parameter)
+        {
+            var parameters = parameter.ToNavigationParameters(TargetElement);
+
+            IsNavigating = true;
+            try
+            {
+                RaiseCanExecuteChanged();
+
+                var navigationService = Navigation.GetNavigationService(SourcePage);
+                await HandleNavigation(parameters, navigationService);
+            }
+            catch (Exception ex)
+            {
+                Log(ex, parameters);
+            }
+            finally
+            {
+                IsNavigating = false;
+                RaiseCanExecuteChanged();
+            }
+        }
+
+        protected async Task HandleNavigation(INavigationParameters parameters, INavigationService navigationService)
+        {
+            var result = await navigationService.SelectTabAsync(Name, parameters);
+            if(!result.Success)
+            {
+                Log(result.Exception, parameters);
+            }
+        }
+
+        protected override ICommand ProvideValue() =>
+            this;
+
+        protected virtual void Log(Exception ex, INavigationParameters parameters)
+        {
+            Xamarin.Forms.Internals.Log.Warning("Warning", $"{GetType().Name} threw an exception");
+            Xamarin.Forms.Internals.Log.Warning("Exception", ex.ToString());
+        }
+
+        protected void RaiseCanExecuteChanged() => CanExecuteChanged?.Invoke(this, EventArgs.Empty);
+    }
+}