如何在 C# 的主线程中生成工作线程并处理它们的输出？

Question

I want to implement the following functionality in C# console application:

1. spawn several worker threads in main thread;
2. each worker thread processes data and send string message to main thread periodically;
3. main thread processes messages and wait for all worker threads to finish;
4. main thread exit.

Now I'm using TPL, but I don't know how to send messages from worker threads to main thread. Thank you for help!

Answer 1

You could use a Producer / Consumer pattern with the TPL as demonstrated in this example on an MSDN blog .

Or, you could kick it old-school and use signaling, see AutoResetEvent .

Or if you care to work at a very low level, use Monitor.Pulse with Monitor.WaitOne (as demonstrated here ).

Either way, you are looking for Synchronization, which you can read up on here .

---

Other option, if you don't actually care what thread the update is running on, would be to take a delegate as an argument and print the update there, à la:

static Task<string> ReadFile(string filename, Action<string> updateStatus)
{

    //do stuf synchronously
    return Task<string>.Factory.StartNew(() => {
        System.Threading.Thread.Sleep(1000);
        //do async stuff
        updateStatus("update message");
        //do other stuff
        return "The result";
    });
}

public static void Main(string[] args) 
{
    var getStringTask = ReadFile("File.txt", (update) => {
        Console.WriteLine(update)
    });
    Console.Writeline("Reading file...");
    //do other stuff here
    //getStringTask.Result will wait if not complete
    Console.WriteLine("File contents: {0}", getStringTask.Result);
}

would print:

Reading file...
update message
File contents: The result

The "update message" call to Console.WriteLine would still occur on the ThreadPool thread, but it may still fill your need.

Answer 2

I would wrap the worker threads to their own Func or regular method with IEnumerable<string> as their return type. Then I'll create a Task for each worker that call foreach on the Func /method and process their message.

Here's a simple example using two regular methods. Should the methods are arbitrary, you'll want to create a List<Task>

static void Main(string[] args)
{
    var task1 = Task.Factory.StartNew(()=>{foreach (var n in Back1(13)) Console.WriteLine("From Back 1, said "+n);});
    var task2 = Task.Factory.StartNew(() => { foreach (var n in Back2(5)) Console.WriteLine("From Back 2, said " + n); });
    task1.Wait();
    task2.Wait();
    Console.WriteLine("All done");
    Console.ReadLine();
}

static IEnumerable<string> Back1(int it)
{
    for (int i = 0; i < it; i++)
    {
        System.Threading.Thread.Sleep(100);
        yield return i +" of "+it;
    }

    yield return "I'm done";
}

static IEnumerable<string> Back2(int it)
{
    for (int i = 0; i < it; i++)
    {
        System.Threading.Thread.Sleep(150);
        yield return i +" of "+it;
    }

    yield return "I'm done";
}