Assembly: System.Windows (in System.Windows.dll)
XMLNS for XAML: Not mapped to an xmlns.
Dependency property identifier field: PointsProperty
A single point, such as (0,0), is a valid value, but will not render anything because you need a minimum of two points to produce a rendered output.
A valid pointSet for the property describes one or more points. As an example of the point set grammar, the string "0,0 50,100 100,0" would produce a "V" shaped polyline with its acute angle placed at 50,100.
A pair of double values that identify the x,y initial point of the polyline.
Subsequent pairs of double values that define additional points of this polyline.
The  characters are not literals; they are indicators of unbounded values. The * also is not literal and indicates that any number of points is permitted past the initial X,Y.
The separator in this grammar can be either a space or a comma. You can use a mixture of space and comma as separators. The common convention is to use commas between the X and Y, and spaces between the points.
Any odd number of double values in a Points value / set of points is not allowed and will throw either a parser or runtime error. The number of double values in the string must always be even so that it evaluates as x,y pairs of points.
The pointSet grammar behavior is implemented by a dedicated native-XAML type converter for PointCollection.