.NET Framework
TPL Dataflow
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Osservazioni
Librerie usate negli esempi
System.Threading.Tasks.Dataflow
System.Threading.Tasks
System.Net.Http
System.Net
Differenza tra Post e SendAsync
Per aggiungere elementi a un blocco puoi utilizzare Post
o SendAsync
.
Post
proverà ad aggiungere l'elemento in modo sincrono e restituirà un bool
dice se è riuscito o meno. Potrebbe non riuscire quando, ad esempio, un blocco ha raggiunto la sua BoundedCapcity
e non ha più spazio per nuovi elementi ancora. SendAsync
altra parte SendAsync
restituirà un Task<bool>
che è possibile await
. Tale attività verrà completata in futuro con un risultato true
quando il blocco ha cancellato la coda interna e può accettare più articoli o con un risultato false
se declina in modo permanente (ad es. A seguito di annullamento).
Pubblicazione su ActionBlock e in attesa di completamento
// Create a block with an asynchronous action
var block = new ActionBlock<string>(async hostName =>
{
IPAddress[] ipAddresses = await Dns.GetHostAddressesAsync(hostName);
Console.WriteLine(ipAddresses[0]);
});
block.Post("google.com"); // Post items to the block's InputQueue for processing
block.Post("reddit.com");
block.Post("stackoverflow.com");
block.Complete(); // Tell the block to complete and stop accepting new items
await block.Completion; // Asynchronously wait until all items completed processingu
Collegamento di blocchi per creare una pipeline
var httpClient = new HttpClient();
// Create a block the accepts a uri and returns its contents as a string
var downloaderBlock = new TransformBlock<string, string>(
async uri => await httpClient.GetStringAsync(uri));
// Create a block that accepts the content and prints it to the console
var printerBlock = new ActionBlock<string>(
contents => Console.WriteLine(contents));
// Make the downloaderBlock complete the printerBlock when its completed.
var dataflowLinkOptions = new DataflowLinkOptions {PropagateCompletion = true};
// Link the block to create a pipeline
downloaderBlock.LinkTo(printerBlock, dataflowLinkOptions);
// Post urls to the first block which will pass their contents to the second one.
downloaderBlock.Post("http://youtube.com");
downloaderBlock.Post("http://github.com");
downloaderBlock.Post("http://twitter.com");
downloaderBlock.Complete(); // Completion will propagate to printerBlock
await printerBlock.Completion; // Only need to wait for the last block in the pipeline
Produttore / consumatore sincrono con BufferBlock
public class Producer
{
private static Random random = new Random((int)DateTime.UtcNow.Ticks);
//produce the value that will be posted to buffer block
public double Produce ( )
{
var value = random.NextDouble();
Console.WriteLine($"Producing value: {value}");
return value;
}
}
public class Consumer
{
//consume the value that will be received from buffer block
public void Consume (double value) => Console.WriteLine($"Consuming value: {value}");
}
class Program
{
private static BufferBlock<double> buffer = new BufferBlock<double>();
static void Main (string[] args)
{
//start a task that will every 1 second post a value from the producer to buffer block
var producerTask = Task.Run(async () =>
{
var producer = new Producer();
while(true)
{
buffer.Post(producer.Produce());
await Task.Delay(1000);
}
});
//start a task that will recieve values from bufferblock and consume it
var consumerTask = Task.Run(() =>
{
var consumer = new Consumer();
while(true)
{
consumer.Consume(buffer.Receive());
}
});
Task.WaitAll(new[] { producerTask, consumerTask });
}
}
Consumatore di produttori asincroni con un buffer buffer limitato
var bufferBlock = new BufferBlock<int>(new DataflowBlockOptions
{
BoundedCapacity = 1000
});
var cancellationToken = new CancellationTokenSource(TimeSpan.FromSeconds(10)).Token;
var producerTask = Task.Run(async () =>
{
var random = new Random();
while (!cancellationToken.IsCancellationRequested)
{
var value = random.Next();
await bufferBlock.SendAsync(value, cancellationToken);
}
});
var consumerTask = Task.Run(async () =>
{
while (await bufferBlock.OutputAvailableAsync())
{
var value = bufferBlock.Receive();
Console.WriteLine(value);
}
});
await Task.WhenAll(producerTask, consumerTask);
Modified text is an extract of the original Stack Overflow Documentation
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