Outer Perimeter of a circular ring

Hello,

i'm using nx open with visual studio 2012 to analyse unkonwn bodies. At the moment i'm searching for a possibility to get the outer perimeter of a circular ring. I already got the totalperimeter (outer plus inner), but i only need the outer perimeter. I can't use the radius because i want the program to work for other shapes too, like a quadrat with inner and outer perimeter.

I hope someone can help me.
Thanks.

If you have NX10 and a SNAP license, you can use the face.OuterLoop property. Then calculate the total length of the edges in this outer loop.