How to avoid recursive dependency properties - wpf

Question

I have a class LineG inherited from a shape which will draw a simple line between two points.. I did that simply by adding two dependency properties StartPointProperty and EndPointProperty... Lastly I want to add another functionality which is MidPoint, so when I draw the line there will be a midPoint in the middle of the line.
When I drag the StartPoint or EndPoint the shape will be redrawn, and when I drag the MidPoint the shape will translate depending on the MidPoint change...
private static void PropertyChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
{
LineG lineG = (LineG)d;
if (e.Property.Name == "StartPoint")
{
}
else if (e.Property.Name == "EndPoint")
{
}
else //if MidPoint
{
Point p1 = (Point)e.OldValue;
Point p2 = (Point)e.NewValue;
double offsetX = p2.X - p1.X;
double offsetY = p2.Y - p1.Y;
lineG.StartPoint = new Point(lineG.StartPoint.X + offsetX, lineG.StartPoint.Y + offsetY);
lineG.EndPoint = new Point(lineG.EndPoint.X + offsetX, lineG.EndPoint.Y + offsetY);
lineG.MidPoint = GeneralMethods.MidPoint(lineG.StartPoint, lineG.EndPoint);
}
lineG.InvalidateMeasure();
}
protected override Geometry DefiningGeometry
{
get
{
lg.StartPoint = StartPoint;
lg.EndPoint = EndPoint;
return lg;
}
}

Answer 1

In such cases you can add an int counter to each operation in your class that you increment during processing. You don't do something if the counter is not 0. Example:
private int _suspendCalculation;
private static void OnPropertyChanged(..)
{
if (_suspendCalculation > 0) return;
_suspendCalculation++;
try
{
CalculateAndSetOtherProperty();
}
finally
{
_suspendCalculation--;
}
}