using System;

using System.Collections.Generic;

using System.Linq;

using System.Linq.Expressions;

​

​

public class Person {

    public string FirstName {get;set;}  

}

​

public class Program

{

    public static void Main()

    {

        var _people = new List<Person>();

        _people.Add(new Person() {FirstName = null});

        _people.Add(new Person() {FirstName = "Robert"});

        _people.Add(new Person() {FirstName = "Bobert"});

        _people.Add(new Person() {FirstName = "Norbert"});

        _people.Add(new Person() {FirstName = "John"});

        _people.Add(new Person() {FirstName = "John"});

        Console.Write("LAMBDA TREE...");            

        Console.WriteLine("person => Concat(person.FirstName, '').ToLower().Contains([SEARCH_TERM])");          

        Expression searchTerm = Expression.Constant("bert");            

        ParameterExpression pe = Expression.Parameter(typeof(Person), "person");        

        Expression lt = Expression.Property(pe, typeof(Person).GetProperty("FirstName"));                       

        // CONCAT

        var strC = Expression.Constant("");

        var methodInfo = typeof(string).GetMethod("Concat", new[] { typeof(string), typeof(string) });

        var concat = Expression.Call(methodInfo, lt, strC);         

        // TOLOWER

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

        // CONTAINS

        var containsExpression = Expression.Call(left, "contains", null, searchTerm);

​

        // final expression

        Console.WriteLine(containsExpression.ToString());

        // compile lambda

        var lambda = Expression.Lambda<Func<Person,bool>>(containsExpression, pe);      

        var compiledLambda = lambda.Compile();

        var result = _people.Where(compiledLambda).ToList();

        foreach (Person p in result) {

            Console.WriteLine("*");

        }

        Console.WriteLine("DONE");

    }

}