using System;

using System.Globalization;

public class Program

{

    public static void Main()

    {

    }

    public enum Unit{

        mm,

        m,

        feet

    }

    public class SAFUnitAttribute : Attribute {

        public Unit ConSteelUnit {get;}

        public Unit SAFMetric {get;}

        public Unit SAFImperial {get;}

        public SAFUnitAttribute(Unit csUnit, Unit safMetric, Unit safImperial){

        //...   

        }

    }

    public class StructuralConnectionPoint {

        [SAFUnit(Unit.mm, Unit.m, Unit.feet)]

        public double X {get;set;}

        [SAFUnit(Unit.mm, Unit.m, Unit.feet)]

        public double Y {get;set;}

        //...

    }

}