Develop Reference

Changing the style of a border inside data template for the listbox item based on the alterationindex [duplicate]

I have seen some articles that show how to use AlternationIndex with ListBoxes or ListViews, but I had spent a few hours trying to get alternating background colors on the base ItemsControl class and nothing seems to work. All ListBox samples I saw use ListBoxItem as the target type for the style that sets the background based onAlternationIndex - like this one from MSDN:
<Grid>
<Grid.Resources>
<Style x:Key="alternatingWithTriggers" TargetType="{x:Type ListBoxItem}">
<Setter Property="Background" Value="Blue"/>
<Setter Property="Foreground" Value="White"/>
<Style.Triggers>
<Trigger Property="ListBox.AlternationIndex" Value="1">
<Setter Property="Background" Value="CornflowerBlue"/>
<Setter Property="Foreground" Value="Black"/>
</Trigger>
<Trigger Property="ListBox.AlternationIndex" Value="2">
<Setter Property="Background" Value="LightBlue"/>
<Setter Property="Foreground" Value="Navy"/>
</Trigger>
</Style.Triggers>
</Style>
</Grid.Resources>
<ListBox AlternationCount="3" ItemsSource="{StaticResource data}"
ItemContainerStyle="{StaticResource alternatingWithTriggers}">
</ListBox>
</Grid>
I want to use the ItemsControl because I do not want the selection functionality and I think restyling a ListBox to hide it might not be the best choice.
This is one of the things I was trying:
<DataTemplate DataType="{x:Type vm:ObservableCollectionItem}">
<Grid>
<!-- some content here -->
</Grid>
</DataTemplate>
<!-- ... -->
<ItemsControl
ItemsSource="{Binding ObservableCollectionItems}"
AlternationCount="2"
>
<ItemsControl.ItemContainerStyle>
<Style>
<Style.Triggers>
<Trigger Property="ItemsControl.AlternationIndex" Value="0">
<Setter Property="Grid.Background" Value="Red"></Setter>
</Trigger>
<Trigger Property="ItemsControl.AlternationIndex" Value="1">
<Setter Property="Grid.Background" Value="Blue"></Setter>
</Trigger>
</Style.Triggers>
</Style>
</ItemsControl.ItemContainerStyle>
</ItemsControl>
The problem I saw was that the visual tree has a list of ContentPresenters that have ItemsControl.AlternationIndex alternate between 0 and 1, but the Grid in each ContentPresenter has ItemsControl.AlternationIndex set to 0.
There is probably something obvious I am missing...

The ItemContainerStyle is applied to the elements generated by the ItemsControl: ContentPresenter. The ContentPresenter will in turn contain whatever you put in your ItemTemplate. In the case of a ListBox, the ItemContainerStyle is applied to the generated ListBoxItem.
The AlternationCount is, based on what you posted, only available on these generated items. You cannot use the ItemContainerStyle to set the Grid's background, because the Grid is unknown to that Style.
The following would be ideal, but unfortunately ContentPresenter has no background property. It would work for a ListBox (with ListBoxItems) however.
<ItemsControl
ItemsSource="{Binding ObservableCollectionItems}"
AlternationCount="2">
<ItemsControl.ItemContainerStyle>
<Style TargetType="ContentPresenter">
<Style.Triggers>
<Trigger Property="ItemsControl.AlternationIndex" Value="0">
<Setter Property="Background" Value="Red"></Setter>
</Trigger>
<Trigger Property="ItemsControl.AlternationIndex" Value="1">
<Setter Property="Background" Value="Blue"></Setter>
</Trigger>
</Style.Triggers>
</Style>
</ItemsControl.ItemContainerStyle>
</ItemsControl>
So you end up writing a style for the grid which binds to the AlternationIndex of your parent ContentPresenter.
<DataTemplate DataType="{x:Type vm:ObservableCollectionItem}">
<Grid>
<Grid.Style>
<Style TargetType="Grid">
<Style.Triggers>
<DataTrigger Binding="{Binding RelativeSource={RelativeSource FindAncestor, AncestorType={x:Type ContentPresenter}}, Path=(ItemsControl.AlternationIndex)}" Value="0">
<Setter Property="Background" Value="Red"/>
</DataTrigger>
<DataTrigger Binding="{Binding RelativeSource={RelativeSource FindAncestor, AncestorType={x:Type ContentPresenter}}, Path=(ItemsControl.AlternationIndex)}" Value="1">
<Setter Property="Background" Value="Blue"/>
</DataTrigger>
</Style.Triggers>
</Style>
</Grid.Style>
</Grid>
</DataTemplate>

hm... After about 2 hours of playing around, I finally found the solution that simply works:
<ItemsControl ItemsSource="{Binding}" AlternationCount="2">
<ItemsControl.ItemTemplate>
<DataTemplate>
<Grid Background="Transparent" x:Name="__PART_GRID"></Grid>
<DataTemplate.Triggers>
<Trigger Property="ItemsControl.AlternationIndex" Value="0">
<Setter TargetName="__PART_GRID" Property="Background" Value="Red"/>
</Trigger>
<Trigger Property="ItemsControl.AlternationIndex" Value="1">
<Setter TargetName="__PART_GRID" Property="Background" Value="Blue"/>
</Trigger>
</DataTemplate.Triggers>
</DataTemplate>
</ItemsControl.ItemTemplate>
</ItemsControl>
I hope this answer helps others to save some time.

Or, as I found on another post, and it works great for me...
You can simply use a binding...
{Binding
RelativeSource={RelativeSource Mode=TemplatedParent},
Path=(ItemsControl.AlternationIndex)}
NB: remember to add AlterationCount="100" on your ItemsControl

I don't know how any of the prior answers are legit. I couldn't make any of them work (didn't try Jacobi's though). Anyways, I found the path to enlightenment here: http://www.dotnetcurry.com/wpf/1211/wpf-items-control-advanced-topic, which lead me to adding the following in the xaml.cs code-behind:
public sealed class CustomItemsControl : ItemsControl
{
protected override DependencyObject GetContainerForItemOverride()
{
return new ContentControl();
}
}
and this in the xaml itself
<local:CustomItemsControl AlternationCount="2"
ItemsSource="{Binding Cells, Mode=OneWay}">
<local:CustomItemsControl.ItemContainerStyle>
<Style TargetType="ContentControl">
<Setter Property="Template">
<Setter.Value>
<ControlTemplate TargetType="ContentControl">
<Border Background="{TemplateBinding Background}">
<ContentPresenter/>
</Border>
</ControlTemplate>
</Setter.Value>
</Setter>
<Style.Triggers>
<Trigger Property="ItemsControl.AlternationIndex" Value="0">
<Setter Property="Background" Value="WhiteSmoke"/>
</Trigger>
<Trigger Property="ItemsControl.AlternationIndex" Value="1">
<Setter Property="Background" Value="LightGray"/>
</Trigger>
</Style.Triggers>
</Style>
</local:CustomItemsControl.ItemContainerStyle>
</local:CustomItemsControl>
This was so damn hard to find a working solution to that I'm actually angry

If you don't want to use the DataTemplate approach, you can create a custom control that uses a ContentControl as the item container, therefore allowing you to specify a background color.
Class:
public class ItemsControlAlternating : ItemsControl
{
static ItemsControlAlternating()
{
DefaultStyleKeyProperty.OverrideMetadata(typeof(ItemsControlAlternating),
new FrameworkPropertyMetadata(typeof(ItemsControlAlternating)));
}
protected override DependencyObject GetContainerForItemOverride()
{
return new ContentControl();
}
protected override bool IsItemItsOwnContainerOverride(object item)
{
return item is ContentControl;
}
}
Resource Dictionary:
<Style TargetType="{x:Type c:ItemsControlAlternating}">
<Setter Property="AlternationCount" Value="2"/>
<Setter Property="Template">
<Setter.Value>
<ControlTemplate TargetType="{x:Type c:ItemsControlAlternating}">
<ItemsPresenter/>
</ControlTemplate>
</Setter.Value>
</Setter>
<Setter Property="ItemContainerStyle">
<Setter.Value>
<Style TargetType="{x:Type ContentControl}">
<Setter Property="Template">
<Setter.Value>
<ControlTemplate TargetType="{x:Type ContentControl}">
<Border Background="{TemplateBinding Background}">
<ContentPresenter/>
</Border>
</ControlTemplate>
</Setter.Value>
</Setter>
<Style.Triggers>
<Trigger Property="ItemsControl.AlternationIndex" Value="0">
<Setter Property="Background" Value="Gray"/>
</Trigger>
<Trigger Property="ItemsControl.AlternationIndex" Value="1">
<Setter Property="Background" Value="White"/>
</Trigger>
</Style.Triggers>
</Style>
</Setter.Value>
</Setter>
</Style>

WPF TreeView - Apply styling based on enum value

I have a TreeView bound to an ObservableCollection containing enum values:
public enum Categories
{
CatA, CatB, CatC, CatD
}
public ObservableCollection<Categories> CategoriesList = new ObservableCollection<Categories>();
foreach (Categories cat in (Categories[])Enum.GetValues(typeof(Categories)))
{
CategoriesList.Add(cat);
}
The TreeView is bound to CategoriesList:
tvCat.ItemsSource = CategoriesList;
The the XAML markup:
<TreeView x:Name="tvCat">
<TreeView.ItemContainerStyle>
<Style TargetType="{x:Type TreeViewItem}">
<Style.Triggers>
<Trigger Property="IsSelected" Value="True">
<Setter Property="FontWeight" Value="Bold"/>
</Trigger>
</Style.Triggers>
</Style>
</TreeView.ItemContainerStyle>
</TreeView>
I am trying to figure out how to apply individual stying to TreeViewItem for each enum value, e.g. blue color for CatA, red color for CatB, may be an icon for CatC etc.
Thanks a lot for any help.

You can use DataTriggers to get the desired output.
<TreeView.ItemContainerStyle>
<Style TargetType="{x:Type TreeViewItem}">
<Style.Triggers>
<Trigger Property="IsSelected" Value="True">
<Setter Property="FontWeight" Value="Bold"/>
</Trigger>
<DataTrigger Binding="{Binding}" Value="CatA">
<Setter Property="Foreground" Value="Blue" />
</DataTrigger>
<DataTrigger Binding="{Binding}" Value="CatB">
<Setter Property="Foreground" Value="Red" />
</DataTrigger>
</Style.Triggers>
</Style>
</TreeView.ItemContainerStyle>
EDIT
The above XAML is if you just want a different color for your Items. If you also want to have different content (e.g. an icon for CatC), then you'd have to set the ControlTemplate based on a DataTrigger.
Here is the XAML to achieve that.
<TreeView.Resources>
<ControlTemplate TargetType="TreeViewItem" x:Key="CatCTemplate">
<Image Source="icon.jpeg" Height="64" Width="64" />
</ControlTemplate>
</TreeView.Resources>
<TreeView.ItemContainerStyle>
<Style TargetType="{x:Type TreeViewItem}">
<Style.Triggers>
<Trigger Property="IsSelected" Value="True">
<Setter Property="FontWeight" Value="Bold"/>
</Trigger>
<DataTrigger Binding="{Binding}" Value="CatA">
<Setter Property="Foreground" Value="Blue" />
</DataTrigger>
<DataTrigger Binding="{Binding}" Value="CatB">
<Setter Property="Foreground" Value="Red" />
</DataTrigger>
<DataTrigger Binding="{Binding}" Value="CatC">
<Setter Property="Template" Value="{StaticResource CatCTemplate}" />
</DataTrigger>
</Style.Triggers>
</Style>
</TreeView.ItemContainerStyle>

Set tooltip max width style

Ok, i know my question might be super dumb- but i couldn't find the solution my self- so here i am- asking your help:
in wpf i have a DataGrid with different styles.
now, i need to set the tooltip max width.
this is my DataGridCell style:
<Style TargetType="DataGridCell" x:Key="MyDataGridCellStyle">
<EventSetter Event="PreviewMouseLeftButtonDown" Handler="DataGridCell_PreviewMouseLeftButtonDown" />
<EventSetter Event="PreviewTextInput" Handler="DataGridCell_PreviewTextInput" />
<Setter Property="FontSize" Value="14" />
<Setter Property="Foreground" Value="Black" />
<Setter Property="Background" Value="White" />
<Setter Property="FontFamily" Value="Arial" />
<Setter Property="Validation.ErrorTemplate" Value="{x:Null}"/>
<Setter Property="ToolTip" Value="{Binding RelativeSource={RelativeSource Self},Path=Content.Text}"/>
</Style>
how do i add to the tooltip the max width style?

Try this please
Keep this code
<Setter Property="ToolTip" Value="{Binding RelativeSource={RelativeSource Self},Path=Content.Text}"/>
and add this to your datagrid
<DataGrid.Resources>
<Style TargetType="ToolTip">
<Setter Property="MaxWidth" Value="20" />
<Setter Property="ContentTemplate">
<Setter.Value>
<DataTemplate>
<ContentPresenter Content="{TemplateBinding Content}" >
<ContentPresenter.Resources>
<Style TargetType="{x:Type TextBlock}">
<Setter Property="TextWrapping" Value="Wrap" />
</Style>
</ContentPresenter.Resources>
</ContentPresenter>
</DataTemplate>
</Setter.Value>
</Setter>
</Style>
</DataGrid.Resources>

Is what you tried to put your tooltip in a textblock
<Setter Property="ToolTip">
<Setter.Value>
<TextBlock MaxWidth="..." TextWrapping="Wrap" Text ="{Binding RelativeSource={RelativeSource Self},Path=Content.Text}"/>
</Setter.Value>
</Setter>

Style list item based on its property

I am pretty new to WPF and I am trying to build a quite simple application using MVVM light.
In my MainWindow.xaml (view) I have this :
<ListBox ItemsSource="{Binding InstalledVersions}"
ItemTemplate="{StaticResource VersionsDataTemplate}"
Style="{StaticResource VersionsStyle}"
ItemContainerStyle="{StaticResource VersionItemStyle}"/>
Where InstalledVersions is a list of InstalledVersionViewModel
In my MainWindowResources.xaml I have this (simplified) :
<DataTemplate x:Key="VersionsDataTemplate"
DataType="{x:Type viewmodels:InstalledVersionViewModel}">
<Grid>
<TextBlock Text="{Binding VersionNumber}" />
<TextBlock Text="{Binding FolderPath}" />
</Grid>
</DataTemplate>
<Style x:Key="VersionsStyle"
TargetType="{x:Type ListBox}">
<Setter Property="HorizontalContentAlignment" Value="Stretch" />
<Setter Property="VerticalContentAlignment" Value="Center" />
</Style>
<Style x:Key="VersionItemStyle"
TargetType="{x:Type ListBoxItem}">
<Setter Property="Background" Value="White" />
</Style>
I wish to have a different background depending on the "IsActive" property of my InstalledVersionViewModel.
I tried to add this (as well as several variations of it) to my VersionItemStyle but (as I suspected, mostly because I don't understand what I'm doing) it doesn't work :
<Style.Triggers>
<Trigger Property="{Binding Path=DataContext.IsActive, RelativeSource={RelativeSource FindAncestor, AncestorType={x:Type viewmodels:InstalledVersionViewModel}}}" Value="True">
<Setter Property="Background" Value="Red" />
</Trigger>
</Style.Triggers>
Thanks !

Since IsActive is part of view model against each row you can achieve that with DataTrigger
<Style x:Key="VersionItemStyle" TargetType="{x:Type ListBoxItem}">
<Setter Property="Background" Value="White" />
<Style.Triggers>
<DataTrigger Binding="{Binding IsActive}" Value="True">
<Setter Property="Background" Value="Red" />
</DataTrigger>
</Style.Triggers>
</Style>

How to reference "PreviousData" when setting ContentPresenter.Style

In the following code I am trying to set the style of the first item in my collection to one template and the rest to a different template by checking if the PreviousElement is null. I think my relativesource is incorrect because the trigger condition is always true. What should the path be?
<DataTemplate x:Key="RowItemTemplate">
<ContentPresenter Content="{Binding}">
<ContentPresenter.Style>
<Style TargetType="{x:Type ContentPresenter}">
<Setter Property="ContentTemplate" Value="{StaticResource ComparisonTemplate}"/>
<Style.Triggers>
<DataTrigger Binding="{Binding RelativeSource={RelativeSource PreviousData}}" Value="{x:Null}">
<Setter Property="ContentTemplate" Value="{StaticResource SourceTemplate}"/>
</DataTrigger>
</Style.Triggers>
</Style>
</ContentPresenter.Style>
</ContentPresenter>
</DataTemplate>

I created an interface that has a bool to determine which template a particular element should use:
<DataTemplate x:Key="RowItemTemplate">
<ContentPresenter Content="{Binding}">
<ContentPresenter.Style>
<Style TargetType="{x:Type ContentPresenter}">
<Setter Property="ContentTemplate" Value="{StaticResource ComparisonTemplate}"/>
<Style.Triggers>
<DataTrigger Binding="{Binding DataItem}" Value="true">
<Setter Property="ContentTemplate" Value="{StaticResource SourceTemplate}"/>
</DataTrigger>
</Style.Triggers>
</Style>
</ContentPresenter.Style>
</ContentPresenter>
</DataTemplate>