Easiest way to make a single statement async in C#?

Question

I've got a single statement running on a ASP.NET page that takes a long time (by long I mean 100ms, which is too long if I want this page to be lightning fast) , and I don't care when it executes as long as executes.

What is the best (and hopefully easiest) way to accomplish this?

Answer 1

If you mean to say that the response can be sent before the command is ran, you could use ThreadPool.QueueUserWorkItem to run it on another thread without blocking your request.

Answer 2

There's a background worker thread that can be very useful when processing information in the background of a .NET application. A bit more context would help answer the question better.

Answer 3

If it's 100ms, then don't bother. Your users can't detect a 100ms delay.

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Edit: some explanations.

If I remember correctly, 100 milliseconds (1/10 second) is near the minimum amount of time that a human can perceive. So, for the purpose of discussion, let me grant that this 100ms can be perceived by the users of the OP's site, and that it is worthwhile to improve performance by 100ms. I assumed from the start that the OP had correctly identified this "long-running" task as a potential source of a 100ms improvement. So, why did I suggest he ignore it?

Dealing with multiple threads properly is not easy, and is a source of bugs that are difficult to track down. Adding threads to a problem is usually not a solution, but is rather a source of other problems you simply don't find right away (*).

I had the opportunity once to learn this the hard way, with a bug that could only be reproduced on the fastest eight-cpu system available at the time, and then only by pounding on the thing relentlessly, while simulating a degree of network failure that would have caused the network administrators to be lined up and shot, if it had happened in real life. The bug turned out to be in the Unix OS kernel handling of signals, and was a matter of the arrangement of a handful of instructions.

Granted I've never seen anything that bad since then, I've still seen many developers tripped up by multithreading bugs. This question, seemed to be, on the one hand, asking for an "easy way out" via threading, and on the other hand, the benefit was only 100ms. Since it did not appear that the OP already had a well-tested threading infrastructure, it seemed to me that it made better sense to ignore the 100ms, or perhaps to pick up performance some other way.

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(*) Of course, there are many circumstances where an algorithm can profitably be made parallel and executed by multiple threads, running on multiple cores. But it does not sound like the OP has such a case.

Answer 4

// This is the delegate to use to execute the process asynchronously
public delegate void ExecuteBackgroundDelegate();

//
[STAThread]
static void Main(string[] args)
{         
    MyProcess proc = new MyProcess();

    // create an instance of our execution delegate
    ExecuteBackgroundDelegate asynchExec = new ExecuteBackgroundDelegate(proc.Execute);

    // execute this asynchronously
    asynchExec.BeginInvoke(null, null);
}

Answer 5

The easiest way is probably to get it to execute in the threadpool. For example, to make this asynchronous:

using System; using System.Threading;

class Test
{
    static void ExecuteLongRunningTask()
    {
        Console.WriteLine("Sleeping...");
        Thread.Sleep(1000);
        Console.WriteLine("... done");
    }

    static void Main()
    {
        ExecuteLongRunningTask();
        Console.WriteLine("Finished");
        Console.ReadLine();
    }
}

Change the first line of Main to:

ThreadPool.QueueUserWorkItem(x => ExecuteLongRunningTask());

Be aware that if you pass any arguments in, they'll be captured variables - that could have subtle side-effects in some cases (particularly if you use it in a loop).

Answer 6

you can use a ThreadPool.

ThreadPool.QueueUserWorkItem( o => Thread.Sleep(1000) /*your long task*/  );

Answer 7

class Test
{
    void LongRunningTask()
    {
        Console.WriteLine("Sleeping...");
        Thread.Sleep(10000);
        Console.WriteLine("... done");
    }

    static void Main()
    {
        Test t = new Test();
        new Action(() => t.LongRunningTask()).BeginInvoke(null, t);
    }
}

Answer 8

I wouldn't bother with any of that threading stuff for a 100ms delay. This will do fine:

protected void Page_Unload(object sender, EventArgs e)
{
    HttpContext.Current.Response.Flush();
    HttpContext.Current.Response.Close();

    // Your code here
}

(copied from my earlier answer for this question)

Since the connection to the client downloading your page will be closed, their browser will stop displaying a loading message. Your code will continue execution normally however.