How to put out a data-bound text block when the property it is bound to has changed using MVVM
I am using the MVVM design pattern and don't want a lot of code in my code. coding in XAML and C #.
when the user saves a new entry, I would like the "entry saved" to appear in the text block, then disappear.
here is what I would like to work:
<TextBlock Name="WorkflowCreated" Text="Record saved">
<TextBlock.Triggers>
<DataTrigger Binding="{Binding Path=NewWorkflowCreated}">
<DataTrigger.EnterActions>
<BeginStoryboard>
<Storyboard>
<DoubleAnimation
Storyboard.TargetName="WorkflowCreated"
Storyboard.TargetProperty="(TextBlock.Opacity)"
From="1.0" To="0.0" Duration="0:0:3"/>
</Storyboard>
</BeginStoryboard>
</DataTrigger.EnterActions>
</DataTrigger>
</TextBlock.Triggers>
so when NewWorkflowCreated is changed in the viewmodel it will trigger an animation, unfortunately it won't work. I also tried this:
<TextBlock Name="Message" Text="This is a test.">
<TextBlock.Triggers>
<EventTrigger RoutedEvent="TextBlock.Loaded">
<BeginStoryboard>
<Storyboard>
<DoubleAnimation
Storyboard.TargetName="Message"
Storyboard.TargetProperty="(TextBlock.Opacity)"
From="1.0" To="0.0" Duration="0:0:3"/>
</Storyboard>
</BeginStoryboard>
</EventTrigger>
</TextBlock.Triggers>
</TextBlock>
any help would be much appreciated. Maybe the View model needs code that requires code?
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3 answers
You are using DataTrigger, which should be styled.
<Window.DataContext>
<WpfApplication2:TestViewModel/>
</Window.DataContext>
<Grid>
<Grid.RowDefinitions>
<RowDefinition/>
<RowDefinition/>
</Grid.RowDefinitions>
<Grid.Resources>
<Style x:Key="textBoxStyle" TargetType="{x:Type TextBlock}">
<Style.Triggers>
<DataTrigger Binding="{Binding Path=NewWorkflowCreated}" Value="True">
<DataTrigger.EnterActions>
<BeginStoryboard>
<Storyboard>
<DoubleAnimation
Storyboard.TargetProperty="(TextBlock.Opacity)"
From="1.0" To="0.0" Duration="0:0:3"/>
</Storyboard>
</BeginStoryboard>
</DataTrigger.EnterActions>
</DataTrigger>
</Style.Triggers>
</Style>
</Grid.Resources>
<TextBlock Name="WorkflowCreated" Style="{StaticResource textBoxStyle}" Text="Record saved" />
<Button Content="press me" Grid.Row="1" Click="Button_Click_1"/>
</Grid>
public class TestViewModel : INotifyPropertyChanged
{
private bool _newWorkflowCreated;
public bool NewWorkflowCreated
{
get { return _newWorkflowCreated; }
set {
_newWorkflowCreated = value;
PropertyChanged(this, new PropertyChangedEventArgs("NewWorkflowCreated"));
}
}
#region Implementation of INotifyPropertyChanged
public event PropertyChangedEventHandler PropertyChanged;
#endregion
}
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Not my blog, but I pretty much found what I was looking for here: https://michaelscherf.wordpress.com/2009/02/23/how-to-trigger-an-animation-when-textblocks-text-is- changed-during-a-databinding /
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