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POCreate objects in worker thread and bind to them
 

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    <p>I've a problem with cross-thread operations in C# / WPF / .NET 4.0.</p> <p><strong>The situation:</strong></p> <p>I have to create a object tree when the user clicks a button and then bind to the tree. Because the creation takes a long time (child objects are recursively instantiated), I used a Thread/BackgroundWorker/Task to prevent the UI from freezing.</p> <p><strong>The problem:</strong></p> <p>I get a XamlParserException (Must create DependencySource on same Thread as the DependencyObject) when binding to the object tree.</p> <p>I understand the problem, but how can it be fixed? I can't create the object tree on the UI thread because this will freeze the UI. But I also can't create the object-tree on another thread because then I'm not able to bind to it.</p> <p>Is there a way to 'marshal' objects to the UI thread?</p> <p><strong>The Event Handler Code</strong> (executed on UI thread)</p> <pre><code> private void OnDiff(object sender, RoutedEventArgs e) { string path1 = this.Path1.Text; string path2 = this.Path2.Text; // Some simple UI updates. this.ProgressWindow.SetText(string.Format( "Comparing {0} with {1}...", path1, path2)); this.IsEnabled = false; this.ProgressWindow.Show(); this.ProgressWindow.Focus(); // The object tree to be created. Comparison comparison = null; Task.Factory.StartNew(() =&gt; { // May take a few seconds... comparison = new Comparison(path1, path2); }).ContinueWith(x =&gt; { // Again some simple UI updates. this.ProgressWindow.SetText("Updating user interface..."); this.DiffView.Items.Clear(); this.Output.Items.Clear(); foreach (Comparison diffItem in comparison.Items) { this.DiffView.Items.Add(diffItem); this.AddOutput(diffItem); } this.Output.Visibility = Visibility.Visible; this.IsEnabled = true; this.ProgressWindow.Hide(); }, CancellationToken.None, TaskContinuationOptions.None, TaskScheduler.FromCurrentSynchronizationContext()); } </code></pre> <p><strong>Example Binding</strong></p> <pre><code> &lt;DataGrid.Columns&gt; &lt;DataGridTemplateColumn CellTemplate="{StaticResource DataGridIconCellTemplate}"/&gt; &lt;DataGridTextColumn Header="Status" Binding="{Binding Path=ItemStatus}"/&gt; &lt;DataGridTextColumn Header="Type" Binding="{Binding Path=ItemType}"/&gt; &lt;DataGridTextColumn Header="Path" Binding="{Binding Path=RelativePath}" Width="*"/&gt; &lt;/DataGrid.Columns&gt; </code></pre> <p>Greetings, Dominik</p>
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    1. COIt would help if you could show some of your code.
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      1. USJohn Bowen
    2. COI added some code snippets to the question via Edit action.
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    3. COyou shouldn't add `[Solved]` to your title or post a solution in your question. You will have to wait 24 hour but you should post the solution in your own answer which you can then accept (again after a delay). This then indicates to the system and other users that the problem is solved.
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      1. USChrisF
 

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