using System;

using System.Linq.Expressions;

using System.Collections;

using System.Collections.Generic;

using System.Linq;

public class Program

{

    public static void Main()

    {

        int initValue = 0;

        int maxValue = 5;

        Console.WriteLine("****************** C# Equivalent Output **************************\n\n");

        for (int cLoopVar = initValue; cLoopVar < maxValue; cLoopVar++)

        {

            Console.WriteLine(cLoopVar);

        }

        Console.WriteLine("\n\n***************** Expression Tree Output **************************\n\n");

        var loopVar = Expression.Parameter(typeof(int), "loopVar");

        var loopBody = Expression.Call(typeof(Console).GetMethod("WriteLine", new[] { typeof(int) }), loopVar);

        var initValueExpr = Expression.Constant(initValue);

        var incrementExpr = Expression.PostIncrementAssign(loopVar);

        var conditionExpr = Expression.LessThan(loopVar, Expression.Constant(maxValue));

        var loop = For(loopVar, initValueExpr, conditionExpr, incrementExpr, loopBody);

        var result = Expression.Lambda<Action<int>>(loop, loopVar).Compile();

        result(initValue);      

    }

    public static Expression For(ParameterExpression loopVar, Expression initValue, Expression condition, Expression increment, Expression loopContent)

    {

        var initAssign = Expression.Assign(loopVar, initValue);

        var breakLabel = Expression.Label("LoopBreak");

        var ifThenElseExpr = Expression.IfThenElse(

            condition,

            Expression.Block(

                loopContent,

                increment

            ),

            Expression.Break(breakLabel)

        );

        var loop = Expression.Loop(ifThenElseExpr, breakLabel);

        var block = Expression.Block(new[] { loopVar },

            initAssign,

            loop

        );

        return block;

    }

}