Wpf How to change List box ItemspanelTemplate using Trigger

As the error say's your trying to set a Style when it's expecting an ItemsPanelTemplate as Setter.Value. Define your resources as ItemPanelTemplate's than ListBox Style's and you should be sorted

Try something like:

<ListBox Name="lv"          Background="LightBlue"          FontSize="12"          ItemsSource="{Binding Source={StaticResource myXmlDataBase},                                XPath=Item}">  <ListBox.Resources>    <ItemsPanelTemplate x:Key="ListBoxWrapTemplate">      <WrapPanel Width="{Binding (FrameworkElement.ActualWidth),                                  RelativeSource={RelativeSource AncestorType=ScrollContentPresenter}}"                  ItemHeight="{Binding (ListView.View).ItemHeight,                                      RelativeSource={RelativeSource AncestorType=ListView}}"                  ItemWidth="{Binding (ListView.View).ItemWidth,                                      RelativeSource={RelativeSource AncestorType=ListView}}" />    </ItemsPanelTemplate>    <ItemsPanelTemplate x:Key="ListBoxHorizontalStackTemplate">          <StackPanel Width="{Binding (FrameworkElement.ActualWidth),                                  RelativeSource={RelativeSource AncestorType=ScrollContentPresenter}}"                  Orientation="Horizontal" />        </ItemsPanelTemplate>    <ItemsPanelTemplate x:Key="ListBoxVerticalStackTemplate">      <StackPanel Width="{Binding (FrameworkElement.ActualWidth),                                  RelativeSource={RelativeSource AncestorType=ScrollContentPresenter}}"                  Orientation="Vertical" />    </ItemsPanelTemplate>  </ListBox.Resources>  <ListBox.Style>    <Style TargetType="ListBox">      <Style.Triggers>        <!--  Your Trigger..  -->        <Trigger Property="Background"                  Value="Green">          <Setter Property="ItemsPanel"                  Value="{DynamicResource ListBoxVerticalStackTemplate}" />        </Trigger>        <Trigger Property="Background"                  Value="LightBlue">          <Setter Property="ItemsPanel"                  Value="{DynamicResource ListBoxHorizontalStackTemplate}" />        </Trigger>        <Trigger Property="Background"                  Value="LightGreen">          <Setter Property="ItemsPanel"                  Value="{DynamicResource ListBoxWrapTemplate}" />        </Trigger>      </Style.Triggers>    </Style>  </ListBox.Style>  ...

I was wondering why Viv's answer did not work in my case :-(Here is what I did wrong:

Do not define the ItemsPanelTemplate appart from the <Style.Triggers> !If you place one in the <Listbox.ItemPanel></Listbox.ItemPanel> the style triggers won't have any effect.

Arnaud.

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