Simple implementation of money for C#

money.cs

namespace Money
{
    public class Money<TCurrency> where TCurrency : ICurrency
    {
        private readonly decimal _value;

        public Money(decimal value)
        {
            _value = value;
        }

        public Money<TCurrency> MultiplyBy(decimal multiplier)
        {
            return new Money<TCurrency>(this._value*multiplier);
        } 

        protected bool Equals(Money<TCurrency> other)
        {
            return _value == other._value;
        }

        public override bool Equals(object obj)
        {
            if (obj is Money<TCurrency>)
            {
                var that = (Money<TCurrency>) obj;
                return this._value == that._value;
            }
            return false;
        }
    }

    public interface ICurrency
    {
    }
    public class Dollar : ICurrency{}
    public class NOK : ICurrency{}
}