Strange behavior scrolling LongListSelector - WP8

Question

I have an app where I save the user's contacts in a local Database, then bind this contacts in a LongListSelector.
The app has a button that,, when clicked, update the local database (make it
identical to the devide).
When there is changes, the LongListSelector has a strange behavior after return from search to the list (view): when I scroll fast or after some time scrolling, a blank space appears in the middle of the list. Then I found out that, apparently, the list
is cutting some items...
This behavior happens only when I have a long list, like 50 items or more..
I bind the items on LongListSelector this way:
XAML:
<Grid x:Name="ContentPanelContatos" Grid.Row="1" Margin="0" VerticalAlignment="Stretch" HorizontalAlignment="Stretch" >
<Grid x:Name="gridContatos" Grid.Row="1" Margin="12,2,12,0" HorizontalAlignment="Stretch" VerticalAlignment="Stretch" >
<Grid.RowDefinitions>
<RowDefinition Height="Auto"/>
<RowDefinition Height="*"/>
</Grid.RowDefinitions>
<Grid Grid.Row="0" Margin="0,0,0,12" >
<TextBox x:Name="tbxSearch" VerticalAlignment="Top" HorizontalAlignment="Stretch" Visibility="Collapsed" TextChanged="TbxSearch_TextChanged" LostFocus="TbxSearch_LostFocus" Style="{StaticResource TextBoxStyle}" />
</Grid>
<phone:LongListSelector Grid.Row="1" x:Name="llsContacts" ItemsSource="{Binding}" SelectionChanged="llsContacts_SelectionChanged" >
<phone:LongListSelector.ItemTemplate>
<DataTemplate>
<ListBoxItem local:TiltEffect.IsTiltEnabled="true">
<Grid Margin="0,0,0,10" >
<TextBlock Text="{Binding NAME, Mode=TwoWay}" FontFamily="Segoe WP" FontSize="28" Margin="77,0,0,0" />
<TextBlock Text="{Binding Path=NUMBER, Mode=TwoWay}" FontFamily="Segoe WP Light" FontSize="17" Margin="77,33,0,0"/>
</Grid>
</ListBoxItem>
</DataTemplate>
</phone:LongListSelector.ItemTemplate>
</phone:LongListSelector>
</Grid>
<!-- more 2 grids with contents -->
</Grid>
I was binding the items using ObservableCollection and I was having this problem.. Then I tried to erase the list and bind it again (after the search) this way:
if (llsContacts.ItemsSource != null)
llsContacts.ItemsSource.Clear();
llsContacts.DataContext = daoRd.GetData();
But I'm still with this problem...
Does anybody can tell me what is happening?
Am I doing something wrong?
Reading this article:
Frame rate counters in Windows Phone, I noticed that when this problem happens, some of the numbers that are on the side of the screen when debugging, stops changing...
They stops like this:
User Interface Thread FPS: 000
Texture Memory Usage: 007181
Surface Counter: 050
Intermediate Texture Counter: 002
Does this numbers means something?

Answer 1

have you dumped the contents of what is returned from daoRD.GetData()?   Could be one of the items in the collection has blank strings?   Also I noticed you clear the ItemsSource before setting the DataContext.  That is probably
not necessary if you are setting the DataContext immediately after that.
Bret Bentzinger (MSFT) @awehellyeah