c# wpf error (System.InvalidOperationException)

Question

namespace WpfApplication1
{
    /// <summary>
    /// Interaction logic for MainWindow.xaml
    /// </summary>
    public partial class MainWindow : Window
    {
        Random random = new Random();

        public MainWindow()
        {
            InitializeComponent();
        }

        private void startButton_Click(object sender, RoutedEventArgs e)
        {
            addEnemy();
        }

        private void addEnemy()
        {
            ContentControl enemy = new ContentControl();
            enemy.Template = Resources["EnemyTemplate"] as ControlTemplate;
            AnimateEnemy(enemy, 0, playArea.ActualWidth - 100, "(canvas.left)");
            AnimateEnemy(enemy, random.Next((int)playArea.ActualHeight - 100), 
                random.Next((int)playArea.ActualHeight - 100), "(canvas.top)");
            playArea.Children.Add(enemy);
        }

        private void AnimateEnemy(ContentControl enemy, double from, double to, string propertyToAnimate)
        {
            Storyboard storyboard = new Storyboard() { AutoReverse = true, RepeatBehavior = RepeatBehavior.Forever };
            DoubleAnimation animation = new DoubleAnimation()
            {
                From = from,
                To = to,
                Duration = new Duration(TimeSpan.FromSeconds(random.Next(4, 6))),
            };
            Storyboard.SetTarget(animation, enemy);
            Storyboard.SetTargetProperty(animation, new PropertyPath(propertyToAnimate));
            storyboard.Children.Add(animation);
              //problem
            storyboard.Begin();
        }

    }

$ My error(An unhandled exception of type 'System.InvalidOperationException' occurred in PresentationFramework.dll

Additional information: Cannot resolve all property references in the property path '(canvas.left)'. Verify that applicable objects support the properties.)

can somebody help me with this?

Try using the case that reflects the actual type/property, eg (Canvas.Left). — Drew Noakes
– Drew Noakes, Commented Jan 8, 2017 at 15:07

mm8 · Accepted Answer · 2017-01-08 20:31:02Z

1

Property names are case-sensitive. It should be Canvas.Left and Canvas.Top:

private void addEnemy()
{
    ContentControl enemy = new ContentControl();
    enemy.Template = Resources["EnemyTemplate"] as ControlTemplate;
    AnimateEnemy(enemy, 0, playArea.ActualWidth - 100, "(Canvas.Left)");
    AnimateEnemy(enemy, random.Next((int)playArea.ActualHeight - 100),
        random.Next((int)playArea.ActualHeight - 100), "(Canvas.Top)");
    playArea.Children.Add(enemy);
}

answered Jan 8, 2017 at 20:31

mm8

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1 Comment

Tolik Kolossov Over a year ago

You are my hero!!! Thnx always forgot look on it... I was thinking I put on redactor some wrong canvas scale or property and focus only it, instead looking what =( Thnx one more time!

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