[Registry Preview] Fix the issue of saving files without truncation (#…

…27113)

src/modules/registrypreview/RegistryPreviewUI/MainWindow.Utilities.cs

@@ -800,7 +800,7 @@ private void SaveFile()
                 FileStreamOptions fileStreamOptions = new FileStreamOptions();
                 fileStreamOptions.Access = FileAccess.Write;
                 fileStreamOptions.Share = FileShare.Write;
-                fileStreamOptions.Mode = FileMode.OpenOrCreate;
+                fileStreamOptions.Mode = FileMode.Create;
 
                 fileStream = new FileStream(App.AppFilename, fileStreamOptions);
                 StreamWriter streamWriter = new StreamWriter(fileStream, System.Text.Encoding.Unicode);