#1,204 – Using a DataTrigger to Change Content in a ContentPresenter
April 6, 2017 4 Comments
You can set the ContentTemplate property of a ContentPresenter to a panel containing some content, using a DataTemplate.
This technique becomes even more useful when you have different types of content to display, depending on a particular state in your application. In the example below, we set up a Style for a ContentPresenter that sets default content for the ContentPresenter and then swaps in entirely different content when the JobDone property in the data context becomes true.
<Window.Resources> <DataTemplate x:Key="DefaultContent"> <StackPanel> <TextBlock Margin="10" Text="Some default content here.."/> <TextBlock Margin="10" Text="Maybe show progress for operation"/> </StackPanel> </DataTemplate> <DataTemplate x:Key="AllDoneContent"> <StackPanel> <TextBlock Margin="10" Text="** This is the ALL DONE content..." Foreground="Green"/> <TextBlock Margin="10" Text="Put anything you like here"/> <Button Margin="10" Content="Click Me" HorizontalAlignment="Left"/> </StackPanel> </DataTemplate> <Style x:Key="MyContentStyle" TargetType="ContentPresenter"> <Setter Property="ContentTemplate" Value="{StaticResource DefaultContent}"/> <Style.Triggers> <DataTrigger Binding="{Binding JobDone}" Value="True"> <Setter Property="ContentTemplate" Value="{StaticResource AllDoneContent}"/> </DataTrigger> </Style.Triggers> </Style> </Window.Resources> <Grid Margin="10"> <Grid.RowDefinitions> <RowDefinition Height="*"/> <RowDefinition Height="Auto"/> <RowDefinition Height="*"/> </Grid.RowDefinitions> <ContentPresenter Grid.Row="0" Style="{StaticResource MyContentStyle}" Content="{Binding}"/> <Separator Grid.Row="1"/> <CheckBox Grid.Row="2" Margin="10" Content="Mark job done" IsChecked="{Binding JobDone}"/> </Grid>
Here’s how the application looks in the two states. Note that we can toggle between the two states using the CheckBox.
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Cleanest implementation out there, except it doesn’t work. The trigger fails to respond
Thank you….. its worthy
Because the code behind, including the JobDone property is missing. Add this and it will work:
using System.ComponentModel;
using System.Windows;
namespace WpfApp1
{
public partial class MainWindow : Window, INotifyPropertyChanged
{
private bool jobDone;
public event PropertyChangedEventHandler PropertyChanged;
protected void NotifyPropertyChanged(string propertyName)
{
if (PropertyChanged != null)
{
PropertyChanged.Invoke(this, new PropertyChangedEventArgs(propertyName));
}
}
public bool JobDone
{
get { return jobDone; }
set
{
jobDone = value;
NotifyPropertyChanged(“JobDone”);
}
}
public MainWindow()
{
InitializeComponent();
this.DataContext = this;
}
}
}