So, I have a requirement to flash a cell (or row) in a XamDataGrid when an error occurs on the underlying model for the cell/row. I’m currently implementing this in code simply because I’ve inherited a new control from the XamDataGrid to handle all my requirements.

I won’t go into the full implementation of the style, but suffice to say the bit that matters looks like this

var style = new Style(typeof (CellValuePresenter));

var trigger = new DataTrigger
{
   Binding = new Binding("DataItem.IsValid"),
   Value = false
};

var animation = new BrushAnimation
{
   From = Brushes.LightPink,
   To = Brushes.Firebrick,
   Duration = TimeSpan.FromSeconds(0.2),
   AutoReverse = true
};

var storyboard = new Storyboard
{
   RepeatBehavior = RepeatBehavior.Forever
};

Storyboard.SetTargetProperty(animation, 
   new PropertyPath(BackgroundProperty));
storyboard.Children.Add(animation);

var enterBeginStoryboard = new BeginStoryboard
{
   Name = "flashingStoryboard",
   Storyboard = storyboard 
};

style.RegisterName("flashingStoryboard", enterBeginStoryboard);

trigger.EnterActions.Add(enterBeginStoryboard);
trigger.ExitActions.Add(
   new StopStoryboard 
   { 
      BeginStoryboardName = "flashingStoryboard" 
   });

style.Triggers.Add(trigger);

In the above code we obviously create the style, with the target type of the CellValuePresenter. Then we’re using a trigger to detect when the view model’s IsValid property is false. This will cause our flashing animation/storyboard to pulse the background brush from light pink to firebrick and back.

Note: The BrushAnimation object is taken from a stackoverflow post Brush to Brush Animation

The creation of the animation and storyboard, hopefully, are fairly self-explanatory. The idea is that when the trigger EnterActions is called the animation begins and when the ExitAction occurs the storyboard is stoppped. We need to supply a name to the StopStoryboard object and here’s where my first mistake was made.

The line style.RegisterName(“flashingStoryboard”, enterBeginStoryboard); is important. Without it we will find that the named storyboard is not found by the StopStoryboard object. The storyboard needs to have the name registered within the
style’s namescope otherwise you’ll get the error I encountered which is an InvalidOperation exception

‘flashingStoryboard’ name cannot be found in the name scope of ‘System.Windows.Style’

This exception will only occur when the StopStoryboard code is called as this is the point it needs to find the object from the namescope.