Hide ListViewItem in WPF ListView - wpf

Question

How can I hide a ListViewItem in a bound ListView? Note: I do not want to remove it.

Answer 1

Yeah, this is easy.
The first thing you need to do is to add a property to the class you are binding to. For example, if you are binding to a User class with FirstName and LastName, just add a Boolean IsSupposedToShow property (you can use any property you like, of course). Like this:
class User: INotifyPropertyChanged
{
public event PropertyChangedEventHandler PropertyChanged;
public string FirstName { get; set; }
public string LastName { get; set; }
private bool m_IsSupposedToShow;
public bool IsSupposedToShow
{
get { return m_IsSupposedToShow; }
set
{
if (m_IsSupposedToShow == value)
return;
m_IsSupposedToShow = value;
if (PropertyChanged != null)
PropertyChanged(this,
new PropertyChangedEventArgs("IsSupposedToShow"));
}
}
}
Then, remember, to hide some item, don't do it in the UI - no no no! Do it in the data. I mean, look for the User record that you want to hide and change that property in it behind the scenes (like in a View Model) - let the UI react. Make the XAML obey the data.
Like this:
<DataTemplate DataType="{x:Type YourType}">
<DataTemplate.Resources>
<Style TargetType="{x:Type TextBlock}">
<Style.Triggers>
<DataTrigger Binding="{Binding IsSupposedToShow}" Value="False">
<Setter Property="Visibility" Value="Collapsed"/>
</DataTrigger>
</Style.Triggers>
</Style>
</DataTemplate.Resources>
<!-- your UI here -->
<TextBlock>
<TextBlock.Text>
<MultiBinding StringFormat="{}{0}, {1}">
<Binding Path="LastName" />
<Binding Path="FirstName" />
</MultiBinding>
</TextBlock.Text>
</TextBlock>
</DataTemplate>
When you change IsSupposedToShow to false, then the XAML understands it is supposed to change the visibility of the whole DataTemplate. It's all wired up for you by WPF and presto, it's what you wanted in your question!
Best of luck!

Answer 2

The approaches that I'd follow, from most to least preferable:
In ListView.ItemContainerStyle, use a DataTrigger to set Visibility based on a bound property.
Use a style in the ItemTemplate, or in the DataTemplate for the items if you're getting default templates from the resource dictionary.
Set the ItemsSource for the ListView to a CollectionView, and handle the CollectionView's Filter event in code-behind. See MSDN's discussion of collection views for details.
Maintain a separate ObservableCollection as the ItemsSource for the ListView and add/remove items as appropriate.
Under no circumstances would I use a ValueConverter, because I have a possibly-irrational distaste for them.
I think that using a CollectionView is probably the most correct way of doing this, but they're kind of inelegant because you have to write an event handler to implement filtering.

Answer 3

Use a style with a trigger to set the items visibility to collapsed.

Answer 4

This page gave me the answer I needed: http://www.abhisheksur.com/2010/08/woring-with-icollectionviewsource-in.html (See section "Filtering".)
Wow, so much easier than XAML.
Example:
bool myFilter(object obj)
{
// Param 'obj' comes from your ObservableCollection<T>.
MyClass c = obj as MyClass;
return c.MyFilterTest();
}
// apply it
myListView.Items.Filter = myFilter;
// clear it
myListView.Items.Filter = null;

Answer 5

The approach with ListView.ItemContainerStyle
<ListView ItemsSource="{Binding Path=Messages}" Grid.Column="1" Grid.Row="1" x:Name="Messages"
SelectedItem="{Binding Path=SelectedMessage, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}" >
<ListView.ItemContainerStyle>
<Style TargetType="{x:Type ListViewItem}">
<Style.Triggers>
<DataTrigger Binding="{Binding IsVisible}" Value="False" >
<Setter Property="Visibility" Value="Collapsed"/>
</DataTrigger>
</Style.Triggers>
</Style>
</ListView.ItemContainerStyle>
<ListView.ItemTemplate >
<DataTemplate>
<StackPanel Orientation="Horizontal" >
<TextBlock VerticalAlignment="Center" >
<TextBlock.Text>
<MultiBinding StringFormat="{}{0} => {1}">
<Binding Path="AuthorName" />
<Binding Path="ReceiverName"/>
</MultiBinding>
</TextBlock.Text>
</TextBlock>
</StackPanel>
</DataTemplate>
</ListView.ItemTemplate>
</ListView>
Jerry Nixon's answer did not work for me completely. I've got to change the xaml a little bit.
Collapsed list view item was using small layout space when I was using DataTemplate.Resources,

Answer 6

<ItemsControl>
<ItemTemplate>
<DataTemplate>
<Image Visibility='{Binding Converter=my:MaybeHideThisElementConverter}' />
</Image>
</DataTemplate>
</ItemTemplate>
</ItemsControl>
What we're doing here is delegating the decision to your implementation of MaybeHideThisElementConverter. This is where you might return Collapsed if the User property of your object is null, or if the Count is an even number, or whatever custom logic your application requires. The converter will be passed each item in your collection, one by one, and you can return either Visibility.Collapsed or Visibility.Visible on a case by case basis.