CODEWITHSUNDEEP
c#wpfdata-bindingtriggersdatatrigger
usefulBee
usefulBee

Reputation: 9702

Simple DataTrigger not Working. Why?

I am trying to change the foreground color of a text block based on a bool property that its value is changed when a button is clicked. However, for some reason this is not working. Also, do I have to add the bool property to a list in first place? I tried adding the bool property directly to the DataContext, but this did not work either. Any help would be appreciated.

    public static bool IsOn { get; set; }

    public static List<bool> boo;

    private void Button_Click(object sender, RoutedEventArgs e)
    {
        IsOn = true;
        boo = new List<bool>();
        boo.Add(IsOn); 
        DataContext = boo;                   
    }

<Window.Resources>

    <Style TargetType="TextBlock">
        <Setter Property="Foreground" Value="Green" />
        <Style.Triggers>
            <DataTrigger Binding="{Binding Path=IsOn}" Value="true">
                <Setter Property="Foreground" Value="Red" />
            </DataTrigger>
        </Style.Triggers>
    </Style>
</Window.Resources>
<Grid>
    <StackPanel>
        <Button Click="Button_Click" Content="Change Color" />
        <TextBlock Name="textBlockColor" Text="My Foreground Color" />
    </StackPanel>

Upvotes: 2

Views: 3047

Answers (1)

kmatyaszek
kmatyaszek

Reputation: 19296

First of all your class must implement INotifyPropertyChanged (msdn) to notify view that your property was changed.

Second you must assign DataContext in MainWindow constructor.

Example:

public partial class MainWindow : Window, INotifyPropertyChanged
{
    public MainWindow()
    {
        InitializeComponent();

        this.DataContext = this;
    }

    private bool _isOn;
    public bool IsOn
    {
        get { return _isOn; }
        set { _isOn = value; OnPropertyChanged("IsOn"); }
    }

    private void Button_Click(object sender, RoutedEventArgs e)
    {
        IsOn = !IsOn;          
    }

    public event PropertyChangedEventHandler PropertyChanged;

    public void OnPropertyChanged(string propName)
    {
        PropertyChangedEventHandler handler = PropertyChanged;
        if (handler != null)
            handler(this, new PropertyChangedEventArgs(propName));
    }
}

Your XAML code is OK.

When your binding doesn't work you should use snoop in the future.

Upvotes: 4

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