其他-补充*号提示文件已更改逻辑

PDF Office/ViewModels/MainContentViewModel.cs

@@ -18,6 +18,7 @@ using System.Threading.Tasks;
 using System.Windows;
 using System.Windows.Controls;
 using PDF_Office.Model;
+using System.ComponentModel;
 
 namespace PDF_Office.ViewModels
 {
@@ -47,7 +48,7 @@ namespace PDF_Office.ViewModels
             }
         }
 
-        private Visibility fileChanged;
+        private Visibility fileChanged = Visibility.Collapsed;
 
         public Visibility FileChanged
         {
@@ -152,6 +153,7 @@ namespace PDF_Office.ViewModels
         {
             PDFViewer = new CPDFViewer();
             PDFViewer.InitDocument(path);
+            PDFViewer.UndoManager.PropertyChanged += UndoManager_PropertyChanged;
             if (PDFViewer.Document == null)
             {
                 //MessageBoxEx.Show(App.MainPageLoader.GetString("Main_OpenFileFailedWarning"));
@@ -192,6 +194,17 @@ namespace PDF_Office.ViewModels
             return true;
         }
 
+        private void UndoManager_PropertyChanged(object sender, PropertyChangedEventArgs e)
+        {
+            if (e.PropertyName == "CanSave")
+            {
+              if( PDFViewer.UndoManager.CanSave)
+                {
+                    FileChanged = Visibility.Visible;
+                }
+            }
+        }
+
         public void OnNavigatedTo(NavigationContext navigationContext)
         {
             if (navigationContext.Parameters.Count <= 0)