gistfile1.cs

using System;

namespace ConsoleApplication61
{
	class Vector
	{
		public int X { get; private set; }

		public Vector() { }

		public Vector(int x)
		{
			X = x;
		}

		public static Vector operator +(Vector lhs, Vector rhs)
		{
			return new Vector(lhs.X + rhs.X);
		}
	}

	class Foo
	{
		private readonly string _worthless;

		public Foo(string worthless)
		{
			_worthless = worthless;
		}

		public static implicit operator Vector(Foo foo)
		{
			return new Vector(foo._worthless.Length);
		}
	}

	class Program
	{
		static void Main()
		{
			var vec1 = new Vector(1);
			var vec2 = new Vector(3);
			Console.WriteLine((vec1 + vec2).X);

			var vec3 = new Vector(5);
			var foo = new Foo("hello, world");
			Console.WriteLine((vec3 + foo).X);
		}
	}
}