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POHow to solve these problems with Asynchronous Callback?
 

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  1. POHow to solve these problems with Asynchronous Callback?
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    <p>I need to run 5 algorithms parallely each takes an image as input and gives image as output. After each of these is done, I need to display the 5 output images. I'm using Asynchronous Callback using delegates for this task.</p> <p>So, I created 5 delegates for these 5 algos and calling them like algo1Delegate.BeginInvoke().</p> <p>Algorithms are running fine and giving the output too. I'm facing 2 problems in displaying these images.</p> <p>For displaying images, I created a class ImageViewer (windows form with picturebox element in it). </p> <pre><code>//ImageViewer constructor ImageViewer(Image img, String Title) { this.pictureBox1.Image = img; this.Text = Title; } </code></pre> <p>I'm displaying images like this: </p> <pre><code>void showImage(Image image, String title) { ImageViewer imageviewer = new ImageViewer(image, title); imageviewer.Show(); } </code></pre> <p>Since I need to display an image after algo. I'm passing <code>new AsyncCallback(showImage)</code> delegate for each of these BeginInvoke() as 3rd parameter </p> <hr> <pre><code>private void showImage(IAsyncResult iasycResult) { MessageBox.Show("white" + Thread.CurrentThread.ManagedThreadId); // Retrieve the `caller` delegate. AsyncResult asycResult = (AsyncResult)iasycResult; caller = (Algo1Delegate)asycResult.AsyncDelegate;//### PROBLEM!!! // Retrieve the string Title that is passed in algodelegate.BeginInvoke(). string title = (string)iasycResult.AsyncState; Image outputImage = caller.EndInvoke(iasycResult); showImage(outputImage, title); } </code></pre> <ol> <li><p>I think you can see the problem in the above callback function. it only works for Algo1 for other 4 alog's it needs to be casted to Algo2Delegate , Algo3Delegate etc.. because asycResult.AsyncDelegate is of type <code>object</code>. How can I solve this problem? How can I make it work for others too?</p></li> <li><p>The imageViewer window is getting "unresponsive". I don't understand why? <code>ImageViewer</code> object is initialized and displayed on the same thread for each of these algos. Why is it becoming unresponsive.</p></li> <li><p>Any other alternative solutions?</p></li> </ol> <p>PS: I cannot declare one delegateType for all the algos since there are some differences in input parameters.</p> <h2>EDIT:</h2> <p>Well, I got enough inputs for my 1st and 3rd questions. I used separate callbacks for each of these algorithms. My 2nd problem is still unsolved. I changed the constructor of ImageViewer() Just to check if they are executing on two different threads:</p> <pre><code> public ImageViewer(Image img, String title) { InitializeComponent(); if (pictureBox1.InvokeRequired) MessageBox.Show("You must Invoke()"); else MessageBox.Show("No need of Invoke()"); this.pictureBox1.Image = img; this.Text = title + " : Image Viewer"; } </code></pre> <p>in every case it says <code>No need of Invoke()</code>. I don't understand what is the problem. Can any one please address this too? I don't get any execptions also. Just the window is becoming unresponsive. I checked if algorithms are causing any trouble. But no, they arent.</p>
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    1. COwhy do you need 5 different types of delegates? Can't you create just one type that you can use for all 5 tasks?
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      1. POHow to solve these problems with Asynchronous Callback?
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    2. CObecause, though algos operate on input image. different algos need different no. of parameters.
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      1. POHow to solve these problems with Asynchronous Callback?
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    3. COClaws, maybe you can regroup these parameters in a single class which would be the parameter for a single delegate
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