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PODatabound ListPicker SelectedItem goes blank when modifying SelectedIndex
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  1. PODatabound ListPicker SelectedItem goes blank when modifying SelectedIndex
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    copied!<p>I have a ListPicker in my Windows Phone 7 app where both the <strong>ItemsSource</strong> and <strong>SelectedIndex</strong> properties are bound to my ViewModel. SelectedIndex is using <strong>Two Way</strong> binding. The items and the SelectedIndex are correctly populated on application startup. However, when I modify the SelectedIndex property in my ViewModel the ListPicker's TextBox goes blank, as if there was no selected item. If I go to full mode and check which is the selected item from the list, the correct item is being selected.</p> <p>Here is the ListPicker xaml code:</p> <pre><code>&lt;toolkit:ListPicker Name="TheListPicker" ItemsSource="{Binding TheItems}" CacheMode="BitmapCache" FullModeHeader="{Binding Path=Resources.TheHeader, Source={StaticResource LocalizedStrings }}" SelectedIndex="{Binding TheCurrentIndex, Mode=TwoWay}" IsEnabled="{Binding IsViewEnabled}" TabIndex="0" &gt; &lt;toolkit:ListPicker.ItemTemplate&gt; &lt;DataTemplate&gt; &lt;StackPanel Orientation="Horizontal" HorizontalAlignment="Center"&gt; &lt;TextBlock Text="{Binding Name}" FontFamily="{StaticResource PhoneFontFamilySemiBold}" FontSize="{StaticResource PhoneFontSizeMediumLarge}" /&gt; &lt;/StackPanel&gt; &lt;/DataTemplate&gt; &lt;/toolkit:ListPicker.ItemTemplate&gt; &lt;toolkit:ListPicker.FullModeItemTemplate&gt; &lt;DataTemplate&gt; &lt;StackPanel x:Name="item" Orientation="Horizontal" Margin="5, 24, 0, 24"&gt; &lt;TextBlock Margin="15, 0, 0, 0" Text="{Binding Name}" FontSize="40" TextWrapping="Wrap" /&gt; &lt;/StackPanel&gt; &lt;/DataTemplate&gt; &lt;/toolkit:ListPicker.FullModeItemTemplate&gt; &lt;/toolkit:ListPicker&gt; </code></pre> <p>This is a simplified version of my ViewModel:</p> <pre><code>[DataMember] public ObservableCollection&lt;ItemEntity&gt; TheItems { get { if (this.theItems == null) { this.theItems = new ObservableCollection&lt;ItemEntity&gt;(); } return this.theItems; } set { this.theItems = value; } } [DataMember] public int TheCurrentIndex { get { return this.theCurrentIndex; } set { if (value != this.theCurrentIndex) { this.theCurrentIndex = value; NotifyPropertyChanged("TheCurrentIndex"); NotifyPropertyChanged("IsSomeOtherPropertyEnabled"); } } } </code></pre> <p>And here is the relevant code from MainPage.xaml.cs (App_ViewModelChanged is an event handler invoked when some async stuff performed on application startup finishes):</p> <pre><code>private void App_ViewModelChanged(object sender, ViewModelChangedEventArgs e) { BindToViewModel(); } private void BindToViewModel() { this.DataContext = this.ViewModel; this.ViewModel.IsViewEnabled = true; } private void SomeAsyncMethodCompleted(object sender, DetectCompletedEventArgs e) { if (e.Error == null) { this.ViewModel.TheCurrentIndex = e.Result; } } </code></pre> <p>This issue is not happening all the time. Happens like 50% of the time. It seems to happen only once in the application lifetime and then never happens again. Also, the issue started appearing when I switched from the Feb 2011 release of the Silverlight Control Toolkit to the Aug 2011 release. Never had this issue before.</p> <p>Is this a known issue?</p>
 

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