save as behavior for svae button

src/modules/registrypreview/RegistryPreviewUILib/RegistryPreviewMainPage.Events.cs

@@ -156,7 +156,28 @@ private async void OpenButton_Click(object sender, RoutedEventArgs e)
         /// </summary>
         private void SaveButton_Click(object sender, RoutedEventArgs e)
         {
+            if (string.IsNullOrEmpty(_appFileName))
+            {
+                // Save out a new REG file and then open it - we have to use the direct Win32 method because FileOpenPicker crashes when it's
+                // called while running as admin
+                IntPtr windowHandle = WinRT.Interop.WindowNative.GetWindowHandle(_mainWindow);
+                string filename = SaveFilePicker.ShowDialog(
+                    windowHandle,
+                    resourceLoader.GetString("SuggestFileName"),
+                    resourceLoader.GetString("FilterRegistryName") + '\0' + "*.reg" + '\0' + resourceLoader.GetString("FilterAllFiles") + '\0' + "*.*" + '\0' + '\0',
+                    resourceLoader.GetString("SaveDialogTitle"));
+
+                if (filename == string.Empty)
+                {
+                    return;
+                }
+
+                _appFileName = filename;
+            }
+
+            // save and update window title
             SaveFile();
+            _updateWindowTitleFunction(_appFileName);
         }
 
         /// <summary>

src/modules/registrypreview/RegistryPreviewUILib/RegistryPreviewMainPage.Utilities.cs

@@ -834,7 +834,12 @@ private async void HandleDirtyClosing(string title, string content, string prima
             {
                 case ContentDialogResult.Primary:
                     // Save, then close
-                    SaveFile();
+                    if (!DirtyCloseSaveFile())
+                    {
+                        // save cancelled
+                        return;
+                    }
+
                     break;
                 case ContentDialogResult.Secondary:
                     // Don't save, and then close!
@@ -850,6 +855,31 @@ private async void HandleDirtyClosing(string title, string content, string prima
             Application.Current.Exit();
         }
 
+        private bool DirtyCloseSaveFile()
+        {
+            if (string.IsNullOrEmpty(_appFileName))
+            {
+                // Save out a new REG file and then open it - we have to use the direct Win32 method because FileOpenPicker crashes when it's
+                // called while running as admin
+                IntPtr windowHandle = WinRT.Interop.WindowNative.GetWindowHandle(_mainWindow);
+                string filename = SaveFilePicker.ShowDialog(
+                    windowHandle,
+                    resourceLoader.GetString("SuggestFileName"),
+                    resourceLoader.GetString("FilterRegistryName") + '\0' + "*.reg" + '\0' + resourceLoader.GetString("FilterAllFiles") + '\0' + "*.*" + '\0' + '\0',
+                    resourceLoader.GetString("SaveDialogTitle"));
+
+                if (filename == string.Empty)
+                {
+                    return false;
+                }
+
+                _appFileName = filename;
+            }
+
+            SaveFile();
+            return true;
+        }
+
         /// <summary>
         /// Method will open the Registry Editor or merge the current REG file into the Registry via the Editor
         /// Process will prompt for elevation if it needs it.