Name: System.Threading.Tasks.Dataflow
Author: Microsoft

About

Provides dataflow components that are collectively referred to as the TPL Dataflow Library. This dataflow model promotes actor-based programming by providing in-process message passing for coarse-grained dataflow and pipelining tasks.

Key Features

Foundation for message passing and parallelizing CPU-intensive and I/O-intensive applications that have high throughput and low latency.
Provides multiple block types for various dataflow operations (e.g., BufferBlock, ActionBlock, TransformBlock).
Dataflow blocks support linking to form networks, allowing you to create complex processing topologies.

How to Use

This sample demonstrates a dataflow pipeline that downloads the book "The Iliad of Homer" from a website and searches the text to match individual words with words that reverse the first word's characters.

using System.Net;
using System.Text.RegularExpressions;
using System.Threading.Tasks.Dataflow;

var nonLetterRegex = new Regex(@"\P{L}", RegexOptions.Compiled);
var client = new HttpClient(new HttpClientHandler { AutomaticDecompression = DecompressionMethods.GZip });

// Setup blocks

// Downloads the requested resource as a string.
TransformBlock<string, string> downloadString = new TransformBlock<string, string>(async uri =>
{
    Console.WriteLine("Downloading '{0}'...", uri);

    return await client.GetStringAsync(uri);
});

// Separates the specified text into an array of words.
TransformBlock<string, string[]> createWordList = new TransformBlock<string, string[]>(text =>
{
    Console.WriteLine("Creating word list...");

    // Remove common punctuation by replacing all non-letter characters with a space character.
    text = nonLetterRegex.Replace(text, " ");

    // Separate the text into an array of words.
    return text.Split(new[] { ' ' }, StringSplitOptions.RemoveEmptyEntries);
});

// Removes short words.
TransformBlock<string[], string[]> filterWordList = new TransformBlock<string[], string[]>(words =>
{
    Console.WriteLine("Filtering word list...");

    return words
       .Where(word => word.Length > 3)
       .ToArray();
});

// Finds all words in the specified collection whose reverse also exists in the collection.
TransformManyBlock<string[], string> findReversedWords = new TransformManyBlock<string[], string>(words =>
{
    Console.WriteLine("Finding reversed words...");

    var wordsSet = new HashSet<string>(words);

    return from word in wordsSet
           let reverse = string.Concat(word.Reverse())
           where word != reverse && wordsSet.Contains(reverse)
           select word;
});

// Prints the provided reversed words to the console.
ActionBlock<string> printReversedWords = new ActionBlock<string>(reversedWord =>
{
    Console.WriteLine("Found reversed words {0}/{1}", reversedWord, string.Concat(reversedWord.Reverse()));
});


// Connect the dataflow blocks to form a pipeline.
var linkOptions = new DataflowLinkOptions { PropagateCompletion = true };

downloadString.LinkTo(createWordList, linkOptions);
createWordList.LinkTo(filterWordList, linkOptions);
filterWordList.LinkTo(findReversedWords, linkOptions);
findReversedWords.LinkTo(printReversedWords, linkOptions);

// Post data to the pipeline, "The Iliad of Homer" by Homer.
downloadString.Post("http://www.gutenberg.org/cache/epub/16452/pg16452.txt");

// Mark the head of the pipeline as complete.
downloadString.Complete();

// Wait for the last block in the pipeline to process all messages.
printReversedWords.Completion.Wait();

// Output:
// Downloading 'http://www.gutenberg.org/cache/epub/16452/pg16452.txt'...
// Creating word list...
// Filtering word list...
// Finding reversed words...
// Found reversed words parts/strap
// Found reversed words deer/reed
// Found reversed words deem/meed
// Found reversed words flow/wolf
// ...

dotnetframework/System.Threading.Tasks.Dataflowv9.0.11

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