And Now for XAML Completely Different

//
// MarkupScript                                                  
// Author: Tom Englert
// Contact: mail@tom-englert.de
// Copyright (C) 2010 tom-englert.de
//

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace MarkupScript
{
    /// <summary>
    /// Decrement a given value, returns the incremented value.
    /// </summary>
    public class Decrement : Statement, IExpression, IStatement
    {
        /// <summary>
        /// Reference to the value to increment.
        /// </summary>
        public Ref Variable { get; set; }

        public override object OnEvaluate()
        {
            if (Variable == null)
            {
                throw new InvalidOperationException("Decrement needs a value reference.");
            }

            int newValue = (int)ToDouble(Variable.Value);
            Variable.Value = --newValue;
            return newValue;
        }
    }
}