Odtnhj

I want to cache public properties that depend on one or more DependencyProperty values, such that they only get recalculated when the DependencyProperty changes. My class inherits from FrameworkElement and INotifyPropertyChanged. I've followed some portions the answer here Implementing INotifyPropertyChanged. Simplified class:

public class ElementBase : FrameworkElement, INotifyPropertyChanged 
 static ElementBase() 
 WidthProperty.OverrideMetadata(typeof(ElementBase), new FrameworkPropertyMetadata(new PropertyChangedCallback(OnCalculatedValueChanged)));
 HeightProperty.OverrideMetadata(typeof(ElementBase), new FrameworkPropertyMetadata(new PropertyChangedCallback(OnCalculatedValueChanged)));
 

 public event PropertyChangedEventHandler PropertyChanged;
 protected void OnPropertyChanged([CallerMemberName] string propertyName = null) => PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));

 private static void OnCalculatedValueChanged(DependencyObject d, DependencyPropertyChangedEventArgs e) 
 // how can property's string name be avoided
 switch (e.Property.ToString()) // force update of non-dependency properties 
 case "Height": // is there a better way to force the recalculations?
 ((ElementBase)d).HalfHeight = 0.0; // set overwrites with calculated value 
 ((ElementBase)d).Center = new Point(0, 0); // set overwrites with calculated value 
 break;
 case "Width": 
 ((ElementBase)d).HalfWidth = 0.0; // set overwrites with calculated value 
 ((ElementBase)d).Center = new Point(0, 0); // set overwrites with calculated value 
 break;
 default: break;
 
 

 // Caching of the public properties. 
 private double halfWidth; // cached calculated half width
 public double HalfWidth get => halfWidth; set halfWidth = Width / 2.0; 

 private double halfHeight; // cached calculated half height
 public double HalfHeight get => halfHeight; set halfHeight = Height / 2.0; 

 private Point center; // cached calculated center point
 public Point Center get => center; set center = new Point(HalfWidth, HalfHeight); 

What I didn't see is:

1. How to attach to PropertyChangedEventHandler events, so related non DependencyProperty properties to be recalculated?


2. How to avoid use of DependencyProperty string names?


3. 
   PropertyChangedCallback entries for OverRideMetadata of the DependencyProperty work, but is that the best way?

I think what you might be looking for is CoerceValue which was intended just for this. Look it up here.