CODEWITHSUNDEEP
c#wpf
AgainMe
AgainMe

Reputation: 780

Hide item if binded value is null?

I've a ListBox like this:

<ListBox VerticalAlignment="Stretch"
         ItemsSource="{Binding EventInfo}">

inside it I've a DataTemplate with a list of TextBlock:

<ListBox.ItemTemplate>
    <DataTemplate>
        <Grid>
           <Grid.ColumnDefinitions>
               <ColumnDefinition Width="100"/>
               <ColumnDefinition Width="20"/>
           </Grid.ColumnDefinitions>
           <Grid.RowDefinitions>
                <RowDefinition/>
                <RowDefinition/>
           </Grid.RowDefinitions>
          <TextBlock Text="Event:" FontWeight="Bold" Grid.Column="0" Grid.Row="0"/>
          <TextBlock Text="{Binding Name}" FontWeight="Bold" Grid.Column="1" Grid.Row="0"/>
         </Grid>
    </DataTemplate>
 </ListBox.ItemTemplate>
</ListBox>

what I need to do is hide the textblock when for example, the binded value is null. I've associate this stuff:

Event: foo

but in some case the Name is null, I need to hide both TextBlock Event and the binded, is possible do this?

UPDATE:

I'm trying to do this pure in xaml as:

<Style TargetType="TextBlock">
     <Style.Triggers>
          <Trigger Property="Text" Value="">
              <Setter Property="Visibility" Value="Collapsed" />
          </Trigger>
          <Trigger Property="Text" Value="{x:Null}">
              <Setter Property="Visibility" Value="Collapsed" />
          </Trigger>
     </Style.Triggers>
</Style>

The problem's that the application fall in interruption mode and as xaml error I get:

System.Windows.Data Error: 40 : BindingExpression path error: 'Name' property not found on 'object' ''Style' (HashCode=7)'.

this error is repeated for each textblock that I've what am I doing wrong?

Upvotes: 2

Views: 5532

Answers (2)

user6996876
user6996876

Reputation:

You can bind the visibility to a property

Visibility="{Binding IsVisibleName, Converter={StaticResource myBoolToVisibilityConverter}}

through a static bool converter

<local:BooleanToVisibiltyConverter x:Key="myBoolToVisibilityConverter" />

for all the elements that must/can be hidden.

Then converter transforms true into visible

public object Convert(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
{
    bool isVisible = (bool)value;
    return (isVisible ? Visibility.Visible : Visibility.Collapsed);
}

Then you'll set them when the conditions are met, like for example (this is a general idea, I don't know about your specific details) in the Name setter (and you have to configure all the other triggers as well)

public string Name 
{
   get { return name;}
   set 
   { 
      name = value; OnPropertyChanged("Name");
      IsVisibleName = name != null; IsVisibleEvent = event != null && name != null;
   }
}

In pure XAML there are data triggers

<Style.Triggers>
    <DataTrigger Binding="{Binding SomeValue}" Value=" x:Null ">
        <Setter Property="Visibility" Value="Visible"/>
    </DataTrigger>
</Style.Triggers>

Upvotes: 4

ibebbs
ibebbs

Reputation: 1993

While you could use a NullToVisibilityConverter here, you will probably find that there is a suspicious gap in your ListBox where the (collapsed) TextBlock's should be due to padding around the ListBoxItemContainer. Worse still, this "gap" could still be selected by the user.

Although these issues could also be resolved using an approach similar to the NullToVisbilityConverter I would very much encourage you to filter out these values from the EventInfo in your ViewModel where logic about what should be presented to the user (but excluding how it should be presented) should be located.

Upvotes: 2

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