Highlight part of text in textblock not working on all listboxItems

Question

I'm trying to highlight part of text in a textblock from a listbox datatemplate which in turn is bounded to a property of a custom class by using a textbox to search the list for input text.

But the problem is that only part of the items are highlighting (most of the ones visible) but when i maximize the window and try to input another character then suddenly all of them gets highlighted my guess where the problem might be is in this piece of code:

ListBoxItem listboxItemFound= (ListBoxItem)this.listBox1.ItemContainerGenerator.ContainerFromItem(TItem);

Since this method is returning a null when the items are not visible but the items are currently in the listbox.
Somehow I guess the items listboxItem instances are not yet created until you scroll down or maximize to view more items.

XAML DataTemplate:

<DataTemplate>
  <Grid Name="gridOfListbox" Height="25" Margin="0,2">
    <DockPanel Name="dockpanelWithTxtBlock">
      <TextBlock Name="textbloxk" DockPanel.Dock="Left" FontSize="15" TextAlignment="Center">
        <Run Text="" /><Run Background="Yellow" Text="" /><Run Text="{Binding ProductID}" />
      </TextBlock>
    </DockPanel>
  </Grid>
</DataTemplate>

If more code is needed just let me know.
Any help would be greatly appreciated!!
Also if there is any other better way of finding the listboxItem bounded to the custom Item just let me know. Thank you very much!

[Pic of problem] http://i.stack.imgur.com/HViag.png

Yes, ListBoxItems are only created as needed by default. This is to improve memory usage and performance. Why do you need to find the ListBoxItem in order to highlight part of the text in it? — Andy
Hi thanks for your quick reply. Because I need to find the textblock (to highlight text) associated with that listboxItem (which is associated with the custom class) since the textblock is in a dataTemplate and not accessible in code. What do you suggest? Maybe if there is a way to force the creation of all instances of listboxItems? if you need more code I could send you so we get a better understanding. — Merv
@AnjumSKhan True but what if when the user maximize or scroll down or whatever to view more items, the other now visible listboxItems are not partly highlighted where they should be? — Merv
That highlight of empty makes not sense to me. Disable container recycling. — paparazzo

Andy Andy · Accepted Answer · 2016-07-12T16:06:05

One way to fix this is to set VirtualizingStackPanel.IsVirtualizing to false for your ListBox. This will cause all of the items to be created right away. The downside to this is if your ListBox has many items, your program will use more memory (since more items will be created), and could potentially run slower depending on the number of items.

A better solution to consider would be to have multiple DataTemplates for this - one without the highlight, and one with. You can set a DataTemplateSelector for your ListBox (using the ItemTemplateSelector property). The selector can choose which template to use based on if the item matches the search term or not.

The tricky part would be writing the template with the highlighted text. You could probably achieve that by having properties on the object the ListBoxItem is bound to for the text before the highlighted text, the highlighted text, and then the remaining text.

Highlight part of text in textblock not working on all listboxItems

1 Answers