public Flow_asynchronously()
        {
            // Build
            var async = new Asynchronize<IMessage>();
            var throttle = new Throttle_message_flow();
            var handle_exception = new Handle_exception();
            _processMessage = new Process_message();

            Action<IMessage> enqueue = _ => async.Process(_, throttle.Process);

            // Bind
            throttle.Continue += handle_exception.Process;
            handle_exception.Continue += _processMessage.Process;
            handle_exception.UnhandledException += _ => UnhandledException(_);
            _process += enqueue;
            _processMessage.Message += _ => Message(_);
            _processMessage.Continue += enqueue;
            _processMessage.Result += _ => Result(_);
            _processMessage.UnhandledException += _ => UnhandledException(_);

            _execute += _processMessage.Execute;

            _start += async.Start;
            _stop += async.Stop;
            _throttle += throttle.Delay;
        }
        public IndexFiles()
        {
            // Build
            var crawlDirTree = new Crawl_directory_tree();
            var compileFiles = new Compile_files(crawlDirTree);

            var readLines = new Read_text_lines();
            var splitLinesIntoWords = new Split_lines_into_words();
            var readWords = new Read_words(readLines, splitLinesIntoWords);

            var filterWords = new Filter_words();
            var extractWords = new Extract_words(readWords, filterWords);

            var compileWords = new Compile_words();
            var writeIndexToFile = new Write_index_to_file();
            var buildIndex = new Build_index(compileWords, writeIndexToFile);

            var logValidationError = new Log<string>(errMsg => "*** " + errMsg);
            var logException = new Log<Exception>(ex => "*** " + ex.Message + '\n' + ex.StackTrace);

            var handleEx = new HandleException<Tuple<string, string>>();

            var asyncCompileFiles = new Asynchronize<Tuple<string, string>>();
            var asyncBuildIndex = new Asynchronize<Tuple<string, string[]>>();

            var countFilesFound = new CountItemsUntilNullForScatter<string>();
            var parExtractWords = new Parallelize<string>();
            var finishStreamOfFileWordsWithNull = new InsertNullAfterItemsForGather<Tuple<string, string[]>>();

            // Bind
            this.in_Process = _ => asyncCompileFiles.In_Process(_);

            asyncCompileFiles.Out_ProcessSequentially += handleEx.In_Process;
            handleEx.Out_Process += compileFiles.In_Process;
            handleEx.Out_Exception += logException.In_Process;

            logException.Out_Data += _ => this.Out_UnhandledException(_);

            compileFiles.Out_FileFound += countFilesFound.In_Count;
            compileFiles.Out_FileFound += filename =>
                                              {
                                                  if (filename != null)
                                                      this.Out_FileFoundToIndex(filename);
                                              };

            countFilesFound.Out_Counted += parExtractWords.In_Process;
            parExtractWords.Out_ProcessInParallel += extractWords.In_Process;

            countFilesFound.Out_Count += finishStreamOfFileWordsWithNull.In_NumberOfItemsToGather;

            extractWords.Out_WordsExtracted += finishStreamOfFileWordsWithNull.In_Process;
            finishStreamOfFileWordsWithNull.Out_Gather += asyncBuildIndex.In_Process;
            asyncBuildIndex.Out_ProcessSequentially += buildIndex.In_Process;

            compileFiles.Out_IndexFilename += buildIndex.In_IndexFilename;

            compileFiles.Out_ValidationError += logValidationError.In_Process;
            logValidationError.Out_Data += _ => this.Out_ValidationError(_);

            buildIndex.Out_Statistics += _ => this.Out_Statistics(_);
        }