Greeting Everyone I am trying to use the User Coordinate System to create features that change independently of the Global Coordinate System I have the Unit Vector of the such features. I wanted to use UserCoordinateSystem in c# for this application but I cam getting some problems here the code UserCoordinateSystemDefinition oCoordSysDef = default(UserCoordinateSystemDefinition); Inventor.Point oPoint1 = mApp.TransientGeometry.CreatePoint(value1, value2,value3); //Origen Inventor.Point oPoint2 = mApp.TransientGeometry.CreatePoint(u1, u2, u3); //Xdirection Inventor.Point oPoint3 = mApp.TransientGeometry.CreatePoint(.v1, v2, v3); //Ydirection oCoordSysDef.SetByThreePoints(oPoint1 , oPoint2, oPoint3); But I get an error that says exception of type 'System.NullReferenceException' occurred what am I doing wrong thank you for your ideas