WPF ListBoxItem IsSelected property selects only for an instant - wpf

Question

I have a ListBoxItem template with a TextBox element within. When the user clicks the TextBox, I should make the ListBoxItem as the SelectedItem of the ListBox.
<ListBox.ItemTemplate>
<DataTemplate>
<DockPanel Margin="4,0,4,0">
<TextBlock Text="{Binding Path=Value1, Mode=OneWay, UpdateSourceTrigger=PropertyChanged}"
ToolTip="{Binding Path=Hint, Mode=OneWay, UpdateSourceTrigger=PropertyChanged}"
VerticalAlignment="Center" />
<TextBox x:Name="TextField"
Margin="2,0,0,0"
Width="{Binding Path=ActWidth, Mode=OneWay}"
Visibility="{Binding Path=VisibleAct, Mode=OneWay}"
/>
</DockPanel>
</DataTemplate>
</ListBox.ItemTemplate>
I have the following Trigger to make the selection:
<ListBox.Resources>
<Style TargetType="ListBoxItem">
<Style.Triggers>
<Trigger Property="IsKeyboardFocusWithin" Value="True">
<Setter Property="IsSelected" Value="True" />
</Trigger>
</Style.Triggers>
</Style>
</ListBox.Resources>
Unfortunately, it works only for
an instant, when I change the focus, the selection disappears.
If I remove the trigger, it works normally but selecting the TextBox does not trigger the selection.
What should I do to make the selection permanent?

Answer 1

Your sample doesn't work because, if the trigger is false, your ListBoxItem is getting the value as it had before triggering. Your ListBoxItem is like 'ehmm, what I was..'.
So you have to set its SelectedValue by adding a default setter that binds its IsSelected state:
<Style TargetType="ListBoxItem">
<Setter Property="IsSelected" Value="{Binding IsSelected, Mode="OneWay", RelativeSource={RelativeSource Self}}" />
<Style.Triggers>
<Trigger Property="IsKeyboardFocusWithin" Value="True">
<Setter Property="IsSelected" Value="True" />
</Trigger>
</Style.Triggers>
</Style>
Setting default setter for IsSelected as OneWay binding to itself will do the job. It will set IsSelected as it was, when the trigger is false.

Answer 2

You could write some code to set the SelectedItem property of the ListBox. You could handle the GotKeyboardFocus event for the TextBox:
<ListBox x:Name="lb2">
<ListBox.ItemTemplate>
<DataTemplate>
<DockPanel Margin="4,0,4,0">
<TextBlock Text="{Binding Path=Value1, Mode=OneWay, UpdateSourceTrigger=PropertyChanged}"
ToolTip="{Binding Path=Hint, Mode=OneWay, UpdateSourceTrigger=PropertyChanged}"
VerticalAlignment="Center" />
<TextBox x:Name="TextField"
Margin="2,0,0,0"
Width="{Binding Path=ActWidth, Mode=OneWay}"
Visibility="{Binding Path=VisibleAct, Mode=OneWay}"
GotKeyboardFocus="TextField_GotKeyboardFocus"
/>
</DockPanel>
</DataTemplate>
</ListBox.ItemTemplate>
</ListBox>
private void TextField_GotKeyboardFocus(object sender, KeyboardFocusChangedEventArgs e)
{
TextBox textBox = sender as TextBox;
lb2.SelectedItem = textBox.DataContext;
}