AutoCAD .NET :: Internal Angles Of A Polyline?

I have created the following code in VB.NET that i allows you to calculate the internal angle of a polyline. First delivery getting the angle of deflection, a ves obtained 180 you rest this and get the inner corner. All fine, as long as the polyline is the image-1.png. Otherwise, if the polyline is as in the image-2.png there is an error in the vertex B.

That algorithm could follow in order to comply with the correct value. Since later this data i presented it in a table of AutoCAD.
 
Public Shared Function AngleDeflection(ByVal pto3d As Point3dCollection) As ArrayList Dim anguloM As Double = 0 Dim vangl As ArrayList = New ArrayList For i As Integer = 0 To pto3d.Count - 2 Dim V As Integer = pto3d.Count - 2 If i = 0 Then anguloM = Math.Atan2(pto3d.Item(i).Y - pto3d.Item(V).Y, pto3d.Item(i).X - pto3d.Item(V).X) - Math.Atan2(pto3d.Item(i + 1).Y - pto3d.Item(i).Y, pto3d.Item(i + 1).X - pto3d.Item(i).X) vangl.Add(anguloM) Else anguloM = Math.Atan2(pto3d.Item((i - 1) + 1).Y - pto3d.Item(i - 1).Y, pto3d.Item((i - 1) + 1).X - pto3d.Item(i - 1).X) - Math.Atan2(pto3d.Item((i - 1) + 2).Y - pto3d.Item((i - 1) + 1).Y, pto3d.Item((i - 1) + 2).X - pto3d.Item((i - 1) + 1).X) vangl.Add(anguloM) End If Next Return vangl End Function