Question

If I have XAML element that is binded to a data source property and the data source changes faster then the human eye can see I am assuming that the UI also gets re drawn faster then the human eye can see and wasting resources. Would it be a good idea for the property change to raise a flag instead of triggering re-draw of UI and then a timer to trigger the UI redraw if the property was changed? or am I missing how the UI gets re-drawn?

Answer 1

You Could use a delyed invocation of raising the property changed event, maybe like this…

public static class DispatcherExtensions
{
    private static Dictionary<string, DispatcherTimer> timers =
        new Dictionary<string, DispatcherTimer>();
    private static readonly object syncRoot = new object();

    public static void DelayInvoke(this Dispatcher dispatcher, string namedInvocation,
        Action action, TimeSpan delay,
        DispatcherPriority priority = DispatcherPriority.Normal)
    {
        lock (syncRoot)
        {
            RemoveTimer(namedInvocation);
            var timer = new DispatcherTimer(delay, priority, (s, e) => action(), dispatcher);
            timer.Start();
            timers.Add(namedInvocation, timer);
        }
    }


    public static void CancelNamedInvocation(this Dispatcher dispatcher, string namedInvocation)
    {
        lock (syncRoot)
        {
            RemoveTimer(namedInvocation);
        }
    }

    private static void RemoveTimer(string namedInvocation)
    {
        if (!timers.ContainsKey(namedInvocation)) return;
        timers[namedInvocation].Stop();
        timers.Remove(namedInvocation);
    } 


} 

Then

private object _property;  
public object Property  
{  
    get { return _property; }  
    set  
    {  
        if (_property != value)  
        {  
            _property = value;  
            Dispatcher.DelayInvoke("PropertyChanged_Property",(Action)(() =>
            {
                 RaisePropertyChanged("Property");   
            }),TimeSpan.FromMilliseconds(500));

        }  
    }  
}  

Not sure i like it though…