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;
using System.Windows.Markup;
using System.Collections;

namespace MarkupScript
{
    /// <summary>
    /// The Get expression. Returns the value of a variable or array member.
    /// </summary>
    public class Get : Statement, IExpression
    {
        /// <summary>
        /// The name of the variable to access.
        /// </summary>
        public IExpression Variable { get; set; }
        /// <summary>
        /// Optional index of the array element to return. Leave this value empty to access the variable itselve.
        /// </summary>
        public IExpression Index { get; set; }
        /// <summary>
        /// Optional name of the array element to return. Leave this value empty to access the variable itselve.
        /// </summary>
        public IExpression Member { get; set; }

        /// <summary>
        /// Flag to indicate if the function should fail if the variable could not be found. 
        /// If Optional is true no error will be generated when the variable does not exist.
        /// </summary>
        public IExpression Optional { get; set; }

        public Get()
        {
        }

        public Get(IExpression variable)
        {
            this.Variable = variable;
        }

        public override object OnEvaluate()
        {
            string variableName = ToString(TryEvaluate(Variable));
            IVariable variable = ToBoolean(TryEvaluate(this.Optional)) ? TryFindVariable(variableName) : FindVariable(variableName);

            if (variable == null)
                return null;

            if (Index != null)
            {
                return GetIndex(variable.Value, (int)ToDouble(TryEvaluate(Index)));
            }
            else if (Member != null)
            {
                return GetMember(variable.Value, ToString(TryEvaluate(Member)));
            }
            else
            {
                return variable.Value;
            }
        }

        private static object GetIndex(object variable, int index)
        {
            try
            {
                IList list = variable as IList;
                if (list != null)
                {
                    return new ConstantExpression(list[index]).Evaluate();
                }

                IEnumerable enumerable = variable as IEnumerable;
                if (enumerable != null)
                {
                    return new ConstantExpression(enumerable.Cast<object>().ElementAt(index)).Evaluate();
                }
            }
            catch (IndexOutOfRangeException)
            {
            }

            return null;
        }

        private static object GetMember(object variable, string name)
        {
            IEnumerable enumerable = variable as IEnumerable;
            if (enumerable != null)
            {
                IVariable value = enumerable.OfType<IVariable>().FirstOrDefault(e => e.Name == name);
                if (value != null)
                {
                    return value.Value;
                }
            }

            return null;
        }
    }
}