using System;

using System.Collections.Generic;

using System.Linq;

using System.Linq.Expressions;

​

public class Program

{

    public static void Main()

    {

        var people = GetPeople();

        ConsolePeople(GetPeopleFiltered(GetFilter(new FilterRequest

        {

        Male = true

        }

​

        ), people.AsQueryable()));

        ConsolePeople(GetPeopleFiltered(GetFilter(new FilterRequest

        {

        Female = true

        }

​

        ), people.AsQueryable()));

        ConsolePeople(GetPeopleFiltered(GetFilter(new FilterRequest

        {

        Male = true, TwentyToThirty = true

        }

​

        ), people.AsQueryable()));

        ConsolePeople(GetPeopleFiltered(GetFilter(new FilterRequest

        {

        Male = true, Female = true, TwentyToThirty = true, ThirtyToFourty = true, TentoTwenty = true

        }

​

        ), people.AsQueryable()));

    }

​

    public static void ConsolePeople(List<Person> people)

    {

        if (people.Count == 0)

            Console.WriteLine("No people found");

        foreach (var person in people)

        {

            Console.WriteLine(string.Format("FirstName: {0}, LastName: {1}, Age: {2}, Gender: {3}", person.FirstName, person.LastName, person.Age, person.Gender.ToString()));

        }

​

        Console.WriteLine(string.Empty);

    }

​

    public static List<Person> GetPeople()

    {

        var people = new List<Person>();

        people.Add(new Person

        {

        FirstName = "Philip", LastName = "Smith", Age = 29, Gender = GenderEnum.Male

        }

​

        );

        people.Add(new Person

        {

        FirstName = "Joe", LastName = "Blogs", Age = 40, Gender = GenderEnum.Male

        }

​

        );

        people.Add(new Person

        {

        FirstName = "Mary", LastName = "Ann", Age = 10, Gender = GenderEnum.Female

        }

​

        );

        people.Add(new Person

        {

        FirstName = "Lisa", LastName = "Dunn", Age = 60, Gender = GenderEnum.Male

        }

​

        );

        people.Add(new Person

        {

        FirstName = "Terry", LastName = "Banks", Age = 89, Gender = GenderEnum.Male

        }

​

        );

        people.Add(new Person

        {

        FirstName = "John", LastName = "Doe", Age = 32, Gender = GenderEnum.Male

        }

​

        );

        people.Add(new Person

        {

        FirstName = "Sally", LastName = "Shields", Age = 19, Gender = GenderEnum.Female

        }

​

        );

        return people;

    }

​

    public static Expression<Func<Person, bool>> GetFilter(FilterRequest request)

    {

        var filtersOne = new List<Expression<Func<Person, bool>>>();

        var filtersTwo = new List<Expression<Func<Person, bool>>>();

        if (request.Male)

            filtersOne.Add(x => x.Gender == GenderEnum.Male);

        if (request.Female)

            filtersOne.Add(x => x.Gender == GenderEnum.Female);

        if (request.TentoTwenty)

            filtersTwo.Add(x => x.Age >= 10 && x.Age < 20);

        if (request.TwentyToThirty)

            filtersTwo.Add(x => x.Age >= 20 && x.Age < 30);

        if (request.ThirtyToFourty)

            filtersTwo.Add(x => x.Age >= 30 && x.Age < 40);

        if (request.FourtyPlus)

            filtersTwo.Add(x => x.Age >= 40);

        var genderFilter = PredicateBuilder.False<Person>();

        foreach (var filter in filtersOne)

        {

            genderFilter = genderFilter.Or(filter);

        }

​

        var ageFilter = PredicateBuilder.False<Person>();

        foreach (var filter in filtersTwo)

        {

            ageFilter = ageFilter.Or(filter);

        }

​

        var returnFilter = PredicateBuilder.True<Person>();

        if (genderFilter != null && filtersOne.Count > 0)

            returnFilter = returnFilter.And(genderFilter);

        if (ageFilter != null && filtersTwo.Count > 0)

            returnFilter = returnFilter.And(ageFilter);

        return returnFilter;

    }

​

    public static List<Person> GetPeopleFiltered(Expression<Func<Person, bool>> filter, IQueryable<Person> people)

    {

        var query =

            from p in people.Where(filter)select p;

        return query.ToList();

    }

}

​

public class FilterRequest

{

    public bool Male

    {

        get;

        set;

    }

​

    public bool Female

    {

        get;

        set;

    }

​

    public bool TentoTwenty

    {

        get;

        set;

    }

​

    public bool TwentyToThirty

    {

        get;

        set;

    }

​

    public bool ThirtyToFourty

    {

        get;

        set;

    }

​

    public bool FourtyPlus

    {

        get;

        set;

    }

}

​

public class Person

{

    public string FirstName

    {

        get;

        set;

    }

​

    public string LastName

    {

        get;

        set;

    }

​

    public int Age

    {

        get;

        set;

    }

​

    public GenderEnum Gender

    {

        get;

        set;

    }

}

​

public enum GenderEnum

{

    Male,

    Female

}

​

public static class PredicateBuilder

{

    public static Expression<Func<T, bool>> True<T>()

    {

        return f => true;

    }

​

    public static Expression<Func<T, bool>> False<T>()

    {

        return f => false;

    }

​

    public static Expression<Func<T, bool>> Or<T>(this Expression<Func<T, bool>> expr1, Expression<Func<T, bool>> expr2)

    {

        var invokedExpr = Expression.Invoke(expr2, expr1.Parameters.Cast<Expression>());

        return Expression.Lambda<Func<T, bool>>(Expression.OrElse(expr1.Body, invokedExpr), expr1.Parameters);

    }

​

    public static Expression<Func<T, bool>> And<T>(this Expression<Func<T, bool>> expr1, Expression<Func<T, bool>> expr2)

    {

        var invokedExpr = Expression.Invoke(expr2, expr1.Parameters.Cast<Expression>());

        return Expression.Lambda<Func<T, bool>>(Expression.AndAlso(expr1.Body, invokedExpr), expr1.Parameters);

    }

}