.NET threading returns value?

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Returning a value from thread?

I have this code:

//Asynchronously start the Thread to process the Execute command request.
Thread objThread = new Thread(new ParameterizedThreadStart(ExecuteCommandSync));
//Make the thread as background thread.
objThread.IsBackground = true;
//Set the Priority of the thread.
objThread.Priority = ThreadPriority.AboveNormal;
//Start the thread.
objThread.Start(command);

The problem is that ExecuteCommandSync returns a string.

How can i capture the string that is returned and return it?

http://stackoverflow.com/questions/1314155/returning-a-value-from-thread — adt, Jul 04 '11 at 18:54
You're going to need an IAsyncResult to share data between threads. but by its nature an async function cannot return data. I can write you a sample for safely sharing data between threads. What application type is this Console? WinForm? WPF? Web? — Glenn Ferrie, Jul 04 '11 at 18:57

score 6 · Answer 1 · answered Jul 04 '11 at 19:06

I would recommend looking into the TPL in .NET 4. It would allow you to do:

Task<string> resultTask = Task.Factory.StartNew( () => ExecuteCommandSync(state) );

Later, when you need the result, you can access it (which will block if the method isn't completed), by doing:

string results = resultTask.Result;

score 3 · Accepted Answer · answered Jul 04 '11 at 18:55

You cannot use ParameterizedThreadStart if the callback returns something. Try the following:

Thread objThread = new Thread(state => 
{
    string result = ExecuteCommandSync(state);
    // TODO: do something with the returned result
});
//Make the thread as background thread.
objThread.IsBackground = true;
//Set the Priority of the thread.
objThread.Priority = ThreadPriority.AboveNormal;
//Start the thread.
objThread.Start(command);

Also notice that objThread.Start starts the thread and returns immediately. So make sure that the hosting process doesn't end before the thread finishes executing as because you made it a background thread it will be aborted. Otherwise don't make it background thread.

score 1 · Answer 3 · answered Jul 04 '11 at 19:34

From Threading in C# by Joseph Albahari

you can do :

static int Work(string s) { return s.Length; }

static void Main(string[] args)
{
  Func<string, int> method = Work;
  IAsyncResult cookie = method.BeginInvoke ("test", null, null);
  //
  // ... here's where we can do other work in parallel...
  //
  int result = method.EndInvoke (cookie);
  Console.WriteLine ("String length is: " + result);

score 0 · Answer 4 · answered Jul 04 '11 at 18:52

0

You can't.

The thread runs in the background, and only finishes some time after the rest of your code.

answered Jul 04 '11 at 18:52

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.NET threading returns value?

4 Answers4