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POLong running operation - updating UI with BitmapImage doesn't work
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copied!<p>I'm so frustrated trying to solve this. Why is creating threads and updating UI after completing them <strong>so complicated</strong>?! I have tried <a href="http://msdn.microsoft.com/en-us/magazine/cc163328.aspx#S4" rel="nofollow" title="WPF Threads: Build More Responsive Apps With The Dispatcher">this</a>, <a href="http://elegantcode.com/2009/07/03/wpf-multithreading-using-the-backgroundworker-and-reporting-the-progress-to-the-ui/" rel="nofollow" title="Elegant Code » WPF Multithreading: Using the BackgroundWorker and Reporting the Progress to the UI.">this</a> and <a href="http://www.a2zdotnet.com/View.aspx?id=93#.T1L5T4d-fxM" rel="nofollow" title="A2Zdotnet.com - How to Create multithreaded UI application in WPF">this</a> and I still can't get my head around the whole multi-threading thing clearly at all. It was so easy in Java...</p> <p>Anyway here's a <strong>simplified version</strong> of my code as the result of third link:</p> <pre><code>private delegate void SimpleDelegate2(BitmapImage bi); private delegate void SimpleDelegate(string st1, string st2); private void Process(string st1) { try { string st2 = "test st2"; SimpleDelegate del = new SimpleDelegate(LongRunningProcess); del.BeginInvoke(st1, st2, null, null); } catch { //do some failsafe thing } } private void LongRunningProcess(string st1, string st2) { //do some long processing with the strings BitmapImage bi = new BitmapImage();//there will be an actual bitmap here SimpleDelegate2 del1 = delegate(BitmapImage bimg) { ImageControlOnWPFform.Source = bimg; //null; }; this.Dispatcher.BeginInvoke(DispatcherPriority.Send, del1, bi); } </code></pre> <p>The problem here is that I can't set the <code>Source</code> value of the Image control to <code>bimg</code> <strong>but I can set it to <code>null</code>!</strong> Whenever I try to set it to <code>bimg</code> I get the exception that says <em>the calling thread cannot access this object because a different thread owns it</em>. I have also tried setting it directly to <code>bi</code> which also gives the same exception.</p> <p>But I can set the source to <code>null</code> without any problem, which means I can modify the <code>Source</code> value of the Image control. But how do I access <code>bi</code> or <code>bimg</code>? Am I doing something wrong?</p> <p><strong>Also:</strong> I notice that the given arguments of the last <code>BeginInvoke</code> do not match any overload of the method <em>but</em> they are still accepted as valid and works properly. When I point at <code>BeginInvoke</code> I am shown a completely different set of method overloads than the ones that appear when I type a <code>(</code> following the method name. Why?</p>

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