Better global exception handling

Save error now shows a Save as button
Recent list now not changed at every access (only on actual file open)
Some code refactoring

ModernKeePass/App.xaml.cs

@@ -9,6 +9,7 @@ using Windows.UI.Xaml;
 using Windows.UI.Xaml.Controls;
 using Windows.UI.Xaml.Navigation;
 using ModernKeePass.Common;
+using ModernKeePass.Exceptions;
 using ModernKeePass.Interfaces;
 
 // The Blank Application template is documented at http://go.microsoft.com/fwlink/?LinkId=234227
@@ -37,14 +38,17 @@ namespace ModernKeePass
 
         private void OnUnhandledException(object sender, UnhandledExceptionEventArgs unhandledExceptionEventArgs)
         {
-            // TODO: catch only save errors for now, rethrow (do not handle) otherwise
+            // Save the argument exception because it's cleared on first access
             var exception = unhandledExceptionEventArgs.Exception;
-            MessageDialogHelper.ShowErrorDialog(
+            var realException =
                 exception is TargetInvocationException &&
                 exception.InnerException != null
                     ? exception.InnerException
-                    : exception);
+                    : exception;
+
+            if (!(realException is SaveException)) return;
             unhandledExceptionEventArgs.Handled = true;
+            MessageDialogHelper.SaveErrorDialog(realException as SaveException, Database);
         }
 
         /// <summary>

ModernKeePass/Common/DatabaseHelper.cs

@@ -1,6 +1,8 @@
 using System;
 using Windows.Storage;
+using Windows.Storage.AccessCache;
 using Windows.UI.Xaml.Controls;
+using ModernKeePass.Exceptions;
 using ModernKeePass.Interfaces;
 using ModernKeePass.ViewModels;
 using ModernKeePassLib;
@@ -102,7 +104,7 @@ namespace ModernKeePass.Common
             {
                 Status = (int)DatabaseStatus.CompositeKeyError;
             }
-            catch (Exception ex)
+            catch (Exception)
             {
                 Status = (int)DatabaseStatus.Error;
                 throw;
@@ -115,10 +117,22 @@ namespace ModernKeePass.Common
         /// <param name="file">The new database file</param>
         public void Save(StorageFile file)
         {
+            var oldFile = DatabaseFile;
             DatabaseFile = file;
+            try
+            {
                 _pwDatabase.SaveAs(IOConnectionInfo.FromFile(DatabaseFile), true, new NullStatusLogger());
+            }
+            catch
+            {
+                DatabaseFile = oldFile;
+                throw;
+            }
+            finally
+            {
                 Status = (int)DatabaseStatus.Opened;
             }
+        }
 
         /// <summary>
         /// Commit the changes to the currently opened database to file
@@ -126,8 +140,15 @@ namespace ModernKeePass.Common
         public void Save()
         {
             if (_pwDatabase == null || !_pwDatabase.IsOpen) return;
+            try
+            {
                 _pwDatabase.Save(new NullStatusLogger());
             }
+            catch (Exception e)
+            {
+                throw new SaveException(e);
+            }
+        }
 
         /// <summary>
         /// Close the currently opened database
@@ -145,7 +166,7 @@ namespace ModernKeePass.Common
 
         public void CreateRecycleBin()
         {
-            RecycleBin = ((GroupVm)RootGroup).AddNewGroup("Recycle bin");
+            RecycleBin = RootGroup.AddNewGroup("Recycle bin");
             RecycleBin.IsSelected = true;
             RecycleBin.IconSymbol = Symbol.Delete;
         }

ModernKeePass/Common/MessageDialogHelper.cs

@@ -1,18 +1,22 @@
 using System;
+using System.Collections.Generic;
+using Windows.Storage.Pickers;
 using Windows.UI.Popups;
+using ModernKeePass.Exceptions;
+using ModernKeePass.Interfaces;
 
 namespace ModernKeePass.Common
 {
     public static class MessageDialogHelper
     {
-        public static async void ShowDeleteConfirmationDialog(string actionText, string contentText, UICommandInvokedHandler action)
+        public static async void ShowActionDialog(string title, string contentText, string actionButtonText, string cancelButtonText, UICommandInvokedHandler action)
         {
             // Create the message dialog and set its content
-            var messageDialog = new MessageDialog(contentText);
+            var messageDialog = new MessageDialog(contentText, title);
 
             // Add commands and set their callbacks; both buttons use the same callback function instead of inline event handlers
-            messageDialog.Commands.Add(new UICommand(actionText, action));
+            messageDialog.Commands.Add(new UICommand(actionButtonText, action));
-            messageDialog.Commands.Add(new UICommand("Cancel"));
+            messageDialog.Commands.Add(new UICommand(cancelButtonText));
 
             // Set the command that will be invoked by default
             messageDialog.DefaultCommandIndex = 1;
@@ -24,6 +28,22 @@ namespace ModernKeePass.Common
             await messageDialog.ShowAsync();
         }
 
+        public static void SaveErrorDialog(SaveException exception, IDatabase database)
+        {
+            ShowActionDialog("Save error", exception.InnerException.Message, "Save as", "Discard", async command => 
+            {
+                var savePicker = new FileSavePicker
+                {
+                    SuggestedStartLocation = PickerLocationId.DocumentsLibrary,
+                    SuggestedFileName = $"{database.DatabaseFile.DisplayName} - copy"
+                };
+                savePicker.FileTypeChoices.Add("KeePass 2.x database", new List<string> { ".kdbx" });
+
+                var file = await savePicker.PickSaveFileAsync();
+                if (file != null) database.Save(file);
+            });
+        }
+
         public static async void ShowErrorDialog(Exception exception)
         {
             if (exception == null) return;

ModernKeePass/Exceptions/SaveException.cs

@@ -0,0 +1,14 @@
+using System;
+
+namespace ModernKeePass.Exceptions
+{
+    public class SaveException : Exception
+    {
+        public new Exception InnerException { get; }
+
+        public SaveException(Exception exception)
+        {
+            InnerException = exception;
+        }
+    }
+}

ModernKeePass/ModernKeePassApp.csproj

@@ -123,6 +123,7 @@
     <Compile Include="Common\ToastNotificationHelper.cs" />
     <Compile Include="Converters\DiscreteIntToSolidColorBrushConverter.cs" />
     <Compile Include="Converters\NullToBooleanConverter.cs" />
+    <Compile Include="Exceptions\SaveException.cs" />
     <Compile Include="Interfaces\IDatabase.cs" />
     <Compile Include="Interfaces\IHasSelectableObject.cs" />
     <Compile Include="Interfaces\ISelectableModel.cs" />

ModernKeePass/Pages/EntryDetailPage.xaml.cs

@@ -76,7 +76,7 @@ namespace ModernKeePass.Pages
                 ? "Are you sure you want to send this entry to the recycle bin?"
                 : "Are you sure you want to delete this entry?";
             var text = isRecycleBinEnabled ? "Item moved to the Recycle bin" : "Item permanently removed";
-            MessageDialogHelper.ShowDeleteConfirmationDialog("Delete", message, a =>
+            MessageDialogHelper.ShowActionDialog("Warning", message, "Delete", "Cancel", a =>
             {
                 ToastNotificationHelper.ShowMovedToast(Model, "Deleting", text);
                 Model.MarkForDelete();

ModernKeePass/Pages/GroupDetailPage.xaml.cs

@@ -116,7 +116,7 @@ namespace ModernKeePass.Pages
                 ? "Are you sure you want to send the whole group and all its entries to the recycle bin?"
                 : "Are you sure you want to delete the whole group and all its entries?";
             var text = isRecycleBinEnabled ? "Item moved to the Recycle bin" : "Item permanently removed";
-            MessageDialogHelper.ShowDeleteConfirmationDialog("Delete", message, a =>
+            MessageDialogHelper.ShowActionDialog("Warning", message, "Delete", "Cancel", a =>
             {
                 ToastNotificationHelper.ShowMovedToast(Model, "Deleting", text);
                 Model.MarkForDelete();

ModernKeePass/Pages/MainPageFrames/RecentDatabasesPage.xaml

@@ -34,9 +34,13 @@
                     </Grid.ColumnDefinitions>
                     <TextBlock Grid.Row="0" Text="{Binding Name}" Padding="5,0,0,0" />
                     <TextBlock Grid.Row="1" Text="{Binding Path}" Padding="5,0,0,0" FontSize="10" />
-                    <local:CompositeKeyUserControl Grid.Row="2" x:Name="DatabaseUserControl" HorizontalAlignment="Stretch" MinWidth="400" Margin="0,10,0,0" Visibility="{Binding IsSelected, Converter={StaticResource BooleanToVisibilityConverter}}" ValidationChecking="OpenDatabaseUserControl_OnValidationChecking">
+                    <local:CompositeKeyUserControl Grid.Row="2" x:Name="DatabaseUserControl" HorizontalAlignment="Stretch" MinWidth="400" Margin="0,10,0,0" Visibility="{Binding IsSelected, Converter={StaticResource BooleanToVisibilityConverter}}">
                         <interactivity:Interaction.Behaviors>
+                            <core:EventTriggerBehavior EventName="ValidationChecking">
+                                <core:CallMethodAction TargetObject="{Binding}" MethodName="OpenDatabaseFile" />
+                            </core:EventTriggerBehavior>
                             <core:EventTriggerBehavior EventName="ValidationChecked">
+                                <core:CallMethodAction TargetObject="{Binding}" MethodName="UpdateAccessTime" />
                                 <core:NavigateToPageAction TargetPage="ModernKeePass.Pages.GroupDetailPage" />
                             </core:EventTriggerBehavior>
                         </interactivity:Interaction.Behaviors>

ModernKeePass/Pages/MainPageFrames/RecentDatabasesPage.xaml.cs

@@ -1,9 +1,5 @@
 // Pour en savoir plus sur le modèle d'élément Page vierge, consultez la page http://go.microsoft.com/fwlink/?LinkId=234238
 
-using System;
-using Windows.UI.Xaml;
-using ModernKeePass.ViewModels;
-
 namespace ModernKeePass.Pages
 {
     /// <summary>
@@ -11,17 +7,9 @@ namespace ModernKeePass.Pages
     /// </summary>
     public sealed partial class RecentDatabasesPage
     {
-
-        public RecentVm Model => (RecentVm)DataContext;
         public RecentDatabasesPage()
         {
             InitializeComponent();
         }
-
-        private void OpenDatabaseUserControl_OnValidationChecking(object sender, EventArgs e)
-        {
-            var app = (App)Application.Current;
-            app.Database.DatabaseFile = ((RecentItemVm)Model.SelectedItem).DatabaseFile;
-        }
     }
 }

ModernKeePass/ViewModels/Items/RecentItemVm.cs

@@ -1,6 +1,8 @@
-using Windows.Storage;
+using System;
+using Windows.Storage;
 using ModernKeePass.Common;
 using Windows.Storage.AccessCache;
+using Windows.UI.Xaml;
 using ModernKeePass.Interfaces;
 
 namespace ModernKeePass.ViewModels
@@ -27,5 +29,21 @@ namespace ModernKeePass.ViewModels
             get { return _isSelected; }
             set { SetProperty(ref _isSelected, value); }
         }
+
+        public void OpenDatabaseFile()
+        {
+            OpenDatabaseFile((Application.Current as App)?.Database);
+        }
+
+        public void OpenDatabaseFile(IDatabase database)
+        {
+            database.DatabaseFile = DatabaseFile;
+        }
+
+        public async void UpdateAccessTime()
+        {
+            var mru = StorageApplicationPermissions.MostRecentlyUsedList;
+            await mru.GetFileAsync(Token);
+        }
     }
 }

ModernKeePass/ViewModels/RecentVm.cs

@@ -37,13 +37,12 @@ namespace ModernKeePass.ViewModels
 
         public RecentVm()
         {
-            // TODO: opening the files actually changes the MRU order
             var mru = StorageApplicationPermissions.MostRecentlyUsedList;
             foreach (var entry in mru.Entries)
             {
                 try
                 {
-                    var file = mru.GetFileAsync(entry.Token).GetAwaiter().GetResult();
+                    var file = mru.GetFileAsync(entry.Token, AccessCacheOptions.SuppressAccessTimeUpdate).GetAwaiter().GetResult();
                     RecentItems.Add(new RecentItemVm(entry, file));
                 }
                 catch (Exception)