Let me start by saying I am very new to WPF so be gentle.

It seems like this should be easy but I am just missing something. I have implemented INotifyPropertyChanged on a few classes/properties and started binding them to elements in XAML but now I have a little more complex binding to make then updating text or changing a color. What I need is when the Alarm property of my object is set to true I need to change colors, start an animation, create and display other elements in the control. I thought I could just call a function in my control when the property is changed but since WPF hides how an element is "bound" to the model's property I am not sure how to wire that up. Is there a better way to perform this type of more complex response to a property change? If not are there any samples out there? I have not been able to find anything close to what I am looking for but I may not be searching with the correct terms.

• wpf
• data-binding

For complex behaviour in response to a property changed event, you should use the following approach: (I'm typing this freestyle so pardon any minor syntax errors)

class MyClass : INotifyPropertyChanged
{    
    //Presumably you've already done this part
    private object _myProperty = null;
    public object MyProperty
    {
        get { return _myProperty; }
        set
        {
            _myProperty = value;
            NotifyPropertyChanged("MyProperty");
        }
    }

    public MyClass()
    {
        this.PropertyChanged += My_PropertyChanged;
    }

    private void My_PropertyChanged( object sender, PropertyChangedEventArgs e)
    {
        if( e.PropertyName == "MyProperty" )
        {
            //Do Something complicated
        }
    }

What I need is when the Alarm property of my object is set to true I need to change colors, start an animation, create and display other elements in the control.

• Change colors: Bind the Color/Foreground of the element you want to change the color of, to the boolean that sets the alarm, and add an IValueConverter in the binding that returns a Brush based on the boolean.
• Start an animation: Use a (data)trigger on whichever element needs to be animated, in that trigger, use a Storyboard to define the animation you want.
• create and display other elements in the control: that really depends on how well you did your MVVM, if the elements are a visualisation of an ObservableCollection through a ListBox/ListView/ItemsControl (which it should), wire up a Command to whatever sets the alarm on/off (the Button class has a Command property built in, other UIElements may require the use of System.Windows.Interactivity) and in the method that this Command will point to, add a new item to the ObservableCollection, the ItemsControl will automatically reflect the change by adding a new control.

Of course this is just raw information, and you're probably not familiar will all these things, that's when Google comes into play ;)

HTH,

Bab.

Your timer / alarm just needs to update the bound property when it elapses. The property should then raise the PropertyChanged event to notify the GUI to update.

You should take a look at DataTriggers that get fired when a property changes in the view model. The EnterActions and ExitActions will allow you to play a Storyboard when the value of the property changes. Here's an example of how it is used MSDN. You can use a content control and style the Template or ContentTemplate to add all of your elements and have it control the Visibility or Opacity of the other elements.

I don't think you are looking at this right. Your class has logic, does calculation, enforces constraints, and enforces relationships among properties. If you have an alarm hopefully there is some business logic to deal with this and should be done in the class (not the UI). A UI is not built to handle an alarm it is built to display status and actions of that alarm. You will make new control visible in an alarm situation and hide other. On the animation I think you might want to throw an event that you listen for to start the animation. The idea there is that when an alarm is thrown to can register additional handles - you want to separate the business logic from the UI (not pull the business logic into the UI).