using System;

using System.Linq.Expressions;

using System.Collections;

using System.Collections.Generic;

using System.Linq;

public class Program

{

    public static void Main()

    {

        string[] customers = { "Maria Anders", "Ana Trujillo", "Thomas Hardy", "Janine Labrune",

                   "Sven Ottlieb", "Diego Roel", "Eduardo Saavedra", "Patricia McKenna"};

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

​

        var list = customers

            .Where(customer => (customer.ToLower() == "diego roel" || customer.Length <= 12))

            .OrderBy(customer => customer);

​

        DisplayData(list.AsQueryable());

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

        // The IQueryable data to query.  

        IQueryable<String> queryableData = customers.AsQueryable<string>();

​

        // Compose the expression tree that represents the parameter to the predicate.  

        ParameterExpression pe = Expression.Parameter(typeof(string), "customer");

​

        // Create an expression tree that represents the expression 'customer.ToLower() == "diego roel"'.  

        Expression left = Expression.Call(pe, typeof(string).GetMethod("ToLower", System.Type.EmptyTypes));

        Expression right = Expression.Constant("diego roel");

        Expression e1 = Expression.Equal(left, right);

​

        // Create an expression tree that represents the expression 'customer.Length <= 12'.  

        left = Expression.Property(pe, typeof(string).GetProperty("Length"));

        right = Expression.Constant(12, typeof(int));

        Expression e2 = Expression.LessThanOrEqual(left, right);

​

        // Combine the expression trees to create an expression tree that represents the  

        // expression '(customer.ToLower() == "diego roel" || customer.Length <= 12)'.  

        Expression predicateBody = Expression.OrElse(e1, e2);

​

        // Create an expression tree that represents the expression  

        // 'customers.Where(customer => (customer.ToLower() == "diego roel" || customer.Length <= 12))'  

        MethodCallExpression whereCallExpression = Expression.Call(

            typeof(Queryable),

            "Where",

             new Type[] { queryableData.ElementType },

             queryableData.Expression,

             Expression.Lambda<Func<string, bool>>(predicateBody, new ParameterExpression[] { pe }));

        // ***** End Where *****  

​

        // ***** OrderBy(customer => customer) *****  

        // Create an expression tree that represents the expression  

        // 'whereCallExpression.OrderBy(customer => customer)'  

        MethodCallExpression orderByCallExpression = Expression.Call(

            typeof(Queryable),

            "OrderBy",

            new Type[] { queryableData.ElementType, queryableData.ElementType },

            whereCallExpression,

            Expression.Lambda<Func<string, string>>(pe, new ParameterExpression[] { pe }));

            // ***** End OrderBy *****  

​

        // Create an executable query from the expression tree.  

        IQueryable<string> results = queryableData.Provider.CreateQuery<string>(orderByCallExpression);

​

        DisplayData(results);

    }

    private static void DisplayData(IQueryable<string> list)

    {

        foreach (var item in list)

        {

            Console.WriteLine(item);

        }

    }

}