Units of measure in C#

units.cs

using System;
class Unit 
{
	public string Name {get; private set;}
	protected Unit(string name) 
	{
		Name = name;
	}
	
	public static readonly Unit DimensionLess = new Unit(" ");
	public static readonly Unit Meters = new Unit("meters");
	public static readonly Unit Seconds = new Unit("seconds");

	public static Unit operator / (Unit a, Unit b)
	{
		if (a.Name == b.Name) return DimensionLess;
		return new FractionUnit(a, b);
	}

	public static Unit operator * (Unit a, Unit b)
	{
		if (a == DimensionLess) return b;
		if (b == DimensionLess) return a;
		
		var aFrac = a as FractionUnit;
		if (aFrac != null && b == aFrac.Under)
			return aFrac.Over;
		
		var bFrac = b as FractionUnit;
		if (bFrac != null && a == bFrac.Under)
			return bFrac.Over;
		
		return new MultUnit(a, b);
	}
	
	public static Scalar operator * (double a, Unit b) 
	{
		return new Scalar(a, b);
	}
}
class MultUnit : Unit
{
	public Unit A {get; private set;}
	public Unit B {get; private set;}
	public MultUnit(Unit a, Unit b): base(a.Name + "*" + b.Name)
	{
		A = a;
		B = b;
	}
}
class FractionUnit : Unit
{
	public Unit Over {get; private set;}
	public Unit Under {get; private set;}
	public FractionUnit(Unit over, Unit under): base(over.Name + "/" + under.Name)
	{
		Over = over;
		Under = under;
	}
}

class Scalar 
{
	public double Value { get;private set;}
	public Unit Unit {get; private set;}
	public Scalar(double v, Unit u) 
	{
		Value = v;
		Unit = u;
	}
	
	public static Scalar operator + (Scalar a, Scalar b) 
	{
		if (a.Unit != b.Unit) 
		{
			throw new InvalidOperationException(string.Format("cannot add scalars with units {0} and {1}", a.Unit.Name, b.Unit.Name));
		}
		return new Scalar(a.Value + b.Value, a.Unit);
	}
	
	public static Scalar operator - (Scalar a, Scalar b) 
	{
		if (a.Unit != b.Unit) 
		{
			throw new InvalidOperationException(string.Format("cannot subtract scalars with units {0} and {1}", a.Unit.Name, b.Unit.Name));
		}
		return new Scalar(a.Value - b.Value, a.Unit);
	}
	
	public static Scalar operator / (Scalar a, Scalar b) 
	{
		return new Scalar(a.Value / b.Value, a.Unit / b.Unit);
	}

	public static Scalar operator * (Scalar a, Scalar b) 
	{
		return new Scalar(a.Value * b.Value, a.Unit * b.Unit);
	}

	public static Scalar operator * (double a, Scalar b) 
	{
		return new Scalar(a * b.Value, b.Unit);
	}
	
	public static Scalar operator * (Scalar a, double b) 
	{
		return new Scalar(a.Value * b, a.Unit);
	}
	
	public override string ToString() 
	{
		return string.Format("{0} {1}", Value, Unit.Name);
	}
}

public class Program
{
	public static void Main()
	{
		var distance = new Scalar(100, Unit.Meters);
		var time = new Scalar(4, Unit.Seconds);
		Console.WriteLine(distance / time);
		Console.WriteLine((9.8 * (Unit.Meters/Unit.Seconds)) * (10 * Unit.Seconds));
	}
}