Discussion : Attempt to add units to numbers in C# in a simple and clean way

01_Sample_Result.cs

void Main()
{
	var a = (Meter)123 + (Kilometer)2.3 + (Centimeter)1234;
	Console.WriteLine(a.ToString());
	Console.WriteLine(a.To<Kilometer>().ToString());
	Console.WriteLine(a.To<Centimeter>().ToString());
	
	var b = (Meter)2 * (Centimeter)30;
	Console.WriteLine(b.ToString());
	Console.WriteLine(b.ToSurface<Centimeter>().ToString());
}

/*
Prints:

2435.34 Meters
2.43534 Kilometers
243534 Centimeters
0.6 Squared Meter
6000 Squared Centimeters

*/

02_IUnit.cs

public interface IUnit
{
	double Value {get;}
	string Name {get;}
	double Factor {get;}
}

03_Distance.cs

public abstract class Distance : IUnit
{
	public abstract double Value {get;}
	public abstract string Name {get;}
	public abstract double Factor {get;}
	
	public override string ToString()
	{
		string plural = (Value > 1)?"s":"";
		return string.Format("{0} {1}{2}",Value, Name, plural);
	}

        public Distance To<T> () where T : Distance, new()
	{
		var initial =  (Distance)Activator.CreateInstance(typeof(T),new object[]{Value});
		return (Distance)Activator.CreateInstance(typeof(T),new object[]{Value/initial.Factor});
	}
}

04_Surface.cs

public class Surface : Distance
{
	private double _value;
	private string _name;
	private double _factor;
	
	public override double Value {get{return _value;}}
	public override string Name {get{return _name;}}
	public override double Factor {get{return _factor;}}
	
	public Surface()
	{
		
	}
	public Surface(Distance source)
	{
		_value = source.Value;
		_name = "Squared " + source.Name;
		_factor = source.Factor *source.Factor;
	}

        public Surface(double value, double factor, string name)
	{
		_value = value;
		_name = "Squared " + name;
		_factor = factor;
	}
	public Surface ToSurface<T> () where T : Distance, new()
	{
		var initial =  (Distance)Activator.CreateInstance(typeof(T),new object[]{Value});
		return new Surface(Value/(initial.Factor*initial.Factor),initial.Factor,initial.Name);
	}
}

05_SurfaceT.cs

public class Surface<T> : Surface where T : Distance
{
	private double _value;
	private string _name;
	private double _factor;
	
	public override double Value {get{return _value;}}
	public override string Name {get{return _name;}}
	public override double Factor {get{return _factor;}}
	
	public Surface()
	{
		
	}
	public Surface(T source)
	{
		_value = source.Value;
		_name = "Squared " + source.Name;
		_factor = source.Factor *source.Factor;
	}

        public Surface(double value, double factor, string name)
	{
		_value = value;
		_name = "Squared " + name;
		_factor = factor;
	}
}

06_Meter.cs

public class Meter : Distance
	{
		private double _value;
		public override double Value {get{return _value;}}
		public override string Name {get{return "Meter";}}
		public override double Factor {get{return 1;}}
		
		public Meter(double value)
		{
			_value = value;
		}
		
		public static implicit operator Meter(double x)
		{
			return new Meter(x);
		}
		
		public static Meter operator +(Meter c1, Meter c2) 
		{
			return new Meter(c1.Value*c1.Factor + c2.Value*c2.Factor);
		}
		public static Meter operator -(Meter c1, Meter c2) 
		{
			return new Meter(c1.Value*c1.Factor - c2.Value*c2.Factor);
		}
		public static Surface operator *(Meter c1, Meter c2) 
		{
			return new Surface<Meter>(new Meter(c1.Value*c1.Factor * c2.Value*c2.Factor));
		}
		public static double operator /(Meter c1, Meter c2) 
		{
			return (c1.Value*c1.Factor / c2.Value*c2.Factor);
		}
	}
	

07_Kilometer.cs

public class Kilometer : Meter
	{
		public override string Name {get{return "Kilometer";}}
		public override double Factor {get{return 1000;}}
		public Kilometer(double value):base(value)
		{
		}

		public static implicit operator Kilometer(double x)
		{
			return new Kilometer(x);
		}
	}

08_Centimeter.cs

public class Centimeter : Meter
	{
		public override string Name {get{return "Centimeter";}}
		public override double Factor {get{return .01;}}
		public Centimeter (double value):base(value)
		{
		}

		public static implicit operator Centimeter(double x)
		{
			return new Centimeter(x);
		}
	}