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C# async & await

Posted on 2015-01-15
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Last Modified: 2015-01-18
Hi Experts,

I want to enumerate files in a folder and then process each file.  Normally I would have done this by creating a thread and updating the UI after each file was processed with the result.

Now I want to do this in an async and await style... I'm a bit stuck with code that looks a bit like this:

        public async void ProcessActions()
        {
            while (!m_bAllActionsProcessed)
                await Task.Run(() => ProcessNextAction());
        }

        private async Task ProcessNextAction()
        {
            if (m_nCurrentAction >= m_Actions.Count)
            {
                m_bAllActionsProcessed = true;
                return; // done.
            }

            Action<object> action = (object obj) =>
            {
                DirectoryAction directoryAction = m_Actions[m_nCurrentAction];
                DirectoryInfo info = new DirectoryInfo(directoryAction.GetDirectory());
                FileInfo[] files = info.GetFiles("*", directoryAction.GetRecurse() ? SearchOption.AllDirectories : SearchOption.TopDirectoryOnly);
                foreach (FileInfo fileInfo in files)
                    HandleFile(fileInfo);
            };

            // and now -->  also, how do I run this task??

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Thanks!
Mike
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Question by:thready
  • 2
4 Comments
 
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Author Comment

by:thready
ID: 40552754
Somehow I think I'm better off on this one using good old threads....
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LVL 75

Accepted Solution

by:
käµfm³d   👽 earned 250 total points
ID: 40552864
First, you should check out the Channel 9 videos on async/await.

Second, as you'll find out in the videos, you should not be using async void for anything other than an event handler.

Third, async/await is good for I/O-bound operations, not CPU-bound operations. The reading of the files from disk is a good candidate for async/await; the processing of the files depends on what you mean by "processing" as to whether or not async/await makes sense.
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LVL 85

Assisted Solution

by:Mike Tomlinson
Mike Tomlinson earned 250 total points
ID: 40552886
Not sure how things are getting fired off...or how your boolean and "m_nCurrentAction" variable are getting changed,  but try something like this out:
        private async void button1_Click(object sender, EventArgs e)
        {
            button1.Enabled = false;

            while (!m_bAllActionsProcessed) // <-- how is "m_bAllActionsProcessed" getting changed?...
                await Task.Run(() => ProcessNextAction());

            MessageBox.Show("Done!");
            button1.Enabled = true;
        }

        private void ProcessNextAction()
        {
            DirectoryAction directoryAction = m_Actions[m_nCurrentAction]; // <-- how is "m_nCurrentAction" getting changed?...
            DirectoryInfo info = new DirectoryInfo(directoryAction.GetDirectory());
            FileInfo[] files = info.GetFiles("*", directoryAction.GetRecurse() ? SearchOption.AllDirectories : SearchOption.TopDirectoryOnly);
            foreach (FileInfo fileInfo in files)
            {
                label1.Invoke((MethodInvoker)delegate { label1.Text = fileInfo.FullName; }); // some kind of progress update
                HandleFile(fileInfo);
            }   
        }

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Author Closing Comment

by:thready
ID: 40556723
async & await are God's gift to programming.  Thanks for your help!
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