Question

I need to call class method in separate thread. The method has a parameter and a return value.

Details

I have a Form with two TextBoxes. User put value in the first TextBox and get the result in the second one:

 private void tbWord_TextChanged(object sender, TextChangedEventArgs e)
 {
     tbResponce.Text = Wiki.DoWork(tbWord.Text);
 }

The Wiki-class must use Wikipedia API:

public class Wiki
{
    private class State
    {
        public EventWaitHandle eventWaitHandle = new ManualResetEvent(false);
        public String result;
        public String word;
    }

    private static void PerformUserWorkItem( Object stateObject )
    {
        State state = stateObject as State;

        if(state != null)
        {
            Uri address = new Uri("http://en.wikipedia.org/w/api.php?action=opensearch&search=" + state.word);
            HttpWebRequest request = WebRequest.Create(address) as HttpWebRequest;
            HttpWebResponse responce = (HttpWebResponse)request.GetResponse();

            StreamReader myStreamReader = new StreamReader(responce.GetResponseStream(), Encoding.GetEncoding(1251));
            state.result = myStreamReader.ReadToEnd();

            state.eventWaitHandle.Set(); 
        }
    }

    public static String DoWork(String _word)
    {
        State state = new State();
        state.word = _word;

        ThreadPool.QueueUserWorkItem(PerformUserWorkItem, state);
        state.eventWaitHandle.WaitOne();
        return state.result;                   
    }     
}

Problem

When user press keys in the tbWord the main form freeze and wait while Wiki class do all the work.

How can I run DoWork asynchronously?

Answer 1

Or use TPL like this:

private void tbWord_TextChanged(object sender, TextChangedEventArgs e) 
 { 
    Task.Factory.StartNew(() =>
    {
        return Wiki.DoWrok(tbWord.Text);
    }).ContinueWith(taskState =>
    {
        tbResponce.Text = taskState.Result;
    }, TaskScheduler.FromCurrentSynchronizationContext());
 } 

see: http://msdn.microsoft.com/en-us/library/dd997394.aspx