ни разу не видел чтоб внутри функции регионы были.

Ну вот кусочек подобной функции

                        #region Add each top directory separately to zip to display backgroundworker progress
                        foreach (string topDirectoryPath in Directory.GetDirectories(CurrentSessionLabelingSessionDirectory, "*", SearchOption.TopDirectoryOnly))
                        {
                            if (backgroundWorker == null || !backgroundWorker.CancellationPending)
                            {
                                #region Compute percentage in size for each folder in top directory
                                float subDirectorySize = ComputeFolderSize(topDirectoryPath);
                                int percentage = (int)(90 * (subDirectorySize / sessionFolderSize)); // 5% at init, other 5% are added on finish
                                #endregion
                                AddDirectoryToZip(zipArchive, topDirectoryPath);
                                #region Update progress for BackgroundWorker
                                progress += percentage;
                                if (progress > 95)
                                {
                                    progress = 95;
                                }
                                backgroundWorker?.ReportProgress(progress);
                                #endregion
                            }
                        }
                        #endregion