fixed async/await behavior

3 files changed, 27 insertions, 9 deletions

diff --git a/Sandbox/Xamarin/HelloWorld/HelloWorld/HelloWorld/App.cs b/Sandbox/Xamarin/HelloWorld/HelloWorld/HelloWorld/App.cs
index 81eb1bf..b6b187d 100644
--- a/Sandbox/Xamarin/HelloWorld/HelloWorld/HelloWorld/App.cs
+++ b/Sandbox/Xamarin/HelloWorld/HelloWorld/HelloWorld/App.cs
@@ -10,7 +10,7 @@ namespace HelloWorld
     {
         protected override void OnInitialized()
         {
-            NavigationService.NavigateAsync("MyMasterDetail/MyNavigationPage/MainPage", animated: false);
+            NavigationService.NavigateAsync("ViewA", animated: false);
         }
 
         protected override void RegisterTypes()
diff --git a/Sandbox/Xamarin/HelloWorld/ModuleA/ViewModels/ViewAViewModel.cs b/Sandbox/Xamarin/HelloWorld/ModuleA/ViewModels/ViewAViewModel.cs
index 46e3a6c..3fde922 100644
--- a/Sandbox/Xamarin/HelloWorld/ModuleA/ViewModels/ViewAViewModel.cs
+++ b/Sandbox/Xamarin/HelloWorld/ModuleA/ViewModels/ViewAViewModel.cs
@@ -1,4 +1,5 @@
-using Prism.Commands;
+using System;
+using Prism.Commands;
 using Prism.Mvvm;
 using Prism.Navigation;
 
@@ -15,18 +16,27 @@ namespace ModuleA.ViewModels
             set { SetProperty(ref _title, value); }
         }
 
+        private bool _canNavigate = true;
+        public bool CanNavigate
+        {
+            get { return _canNavigate; }
+            set { SetProperty(ref _canNavigate, value); }
+        }
+
         public DelegateCommand NavigateCommand { get; set; }
 
         public ViewAViewModel(INavigationService navigationService)
         {
             _navigationService = navigationService;
 
-            NavigateCommand = new DelegateCommand(Navigate);
+            NavigateCommand = new DelegateCommand(Navigate).ObservesCanExecute((vm) => CanNavigate);
         }
 
-        void Navigate()
+        async void Navigate()
         {
-            _navigationService.NavigateAsync("ViewB");
+            CanNavigate = false;
+            await _navigationService.NavigateAsync("ViewB");
+            CanNavigate = true;
         }
 
         public void OnNavigatedFrom(NavigationParameters parameters)
diff --git a/Sandbox/Xamarin/HelloWorld/ModuleA/ViewModels/ViewBViewModel.cs b/Sandbox/Xamarin/HelloWorld/ModuleA/ViewModels/ViewBViewModel.cs
index ac31c8d..2f697ca 100644
--- a/Sandbox/Xamarin/HelloWorld/ModuleA/ViewModels/ViewBViewModel.cs
+++ b/Sandbox/Xamarin/HelloWorld/ModuleA/ViewModels/ViewBViewModel.cs
@@ -16,18 +16,26 @@ namespace ModuleA.ViewModels
             set { SetProperty(ref _title, value); }
         }
 
+        private bool _canNavigate = true;
+        public bool CanNavigate
+        {
+            get { return _canNavigate; }
+            set { SetProperty(ref _canNavigate, value); }
+        }
+
         public DelegateCommand NavigateCommand { get; set; }
 
         public ViewBViewModel(INavigationService navigationService)
         {
             _navigationService = navigationService;
-
-            NavigateCommand = new DelegateCommand(Navigate);
+            NavigateCommand = new DelegateCommand(Navigate).ObservesCanExecute((vm) => CanNavigate);
         }
 
-        void Navigate()
+        async void Navigate()
         {
-            _navigationService.GoBackAsync();
+            CanNavigate = false;
+            await _navigationService.GoBackAsync();
+            CanNavigate = true;
         }
 
         public void OnNavigatedFrom(NavigationParameters parameters)