How to freeze first item of listbox in wpf? - wpf

Question

I have a listbox with radio button as its items. The listbox is scrollable and can add as many items as possible. But, I have to keep the first item freezed as it should be visible all the time. Any ideas please?

Answer 1

its bit tricky. you can edit the template of Listbox and add a ListBoxItem above the scrollviewer. somthing like
<Style x:Key="ListBoxTopItemFixedStyle" TargetType="{x:Type ListBox}">
<Setter Property="Template">
<Setter.Value>
<ControlTemplate TargetType="{x:Type ListBox}">
<Border x:Name="Bd" BorderBrush="{TemplateBinding BorderBrush}" BorderThickness="{TemplateBinding BorderThickness}" Background="{TemplateBinding Background}" Padding="1" SnapsToDevicePixels="true">
<Grid>
<Grid.RowDefinitions>
<RowDefinition Height="Auto"/>
<RowDefinition Height="*"/>
</Grid.RowDefinitions>
<ListBoxItem Content="{Binding Path=FreezeItem.PropertyName,
RelativeSource={RelativeSource AncestorType={x:Type Window}}}"
Grid.Row="0"/>
<ScrollViewer Focusable="false" Padding="{TemplateBinding Padding}" Grid.Row="1">
<ItemsPresenter SnapsToDevicePixels="{TemplateBinding SnapsToDevicePixels}"/>
</ScrollViewer>
</Grid>
</Border>
<ControlTemplate.Triggers>
<Trigger Property="IsEnabled" Value="false">
<Setter Property="Background" TargetName="Bd" Value="{DynamicResource {x:Static SystemColors.ControlBrushKey}}"/>
</Trigger>
<MultiTrigger>
<MultiTrigger.Conditions>
<Condition Property="IsGrouping" Value="true"/>
<Condition Property="VirtualizingPanel.IsVirtualizingWhenGrouping" Value="false"/>
</MultiTrigger.Conditions>
<Setter Property="ScrollViewer.CanContentScroll" Value="false"/>
</MultiTrigger>
</ControlTemplate.Triggers>
</ControlTemplate>
</Setter.Value>
</Setter>
</Style>
I have also used FreezeItem which is an item from collection in context of control. You can use same concept and modify it as per your need. You can also use converter to get first item of collection if you want to avoid FreezeItem.