How to use Enums with Dynamic Linq?

Question

I would like to use enumerations in my dynamic LINQ queries.

Is it possible, and if, how?

Consider the code bellow:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Linq.Dynamic;

namespace ConsoleApplication2
{
    class Program
    {
        static void Main(string[] args)
        {
            Room aRoom = new Room() { Name = "a Room" };
            Room bRoom = new Room() { Name = "b Room" };
            Room cRoom = new Room() { Name = "c Room" };

            House myHouse = new House
            {
                Rooms = new List<Room>(new Room[] { aRoom }),
                MainRoom = aRoom
            };
            House yourHouse = new House()
            {
                Rooms = new List<Room>(new Room[] { bRoom, cRoom }),
                MainRoom = bRoom
            };
            House donaldsHouse = new House()
            {
                Rooms = new List<Room>(new Room[] { aRoom, bRoom, cRoom }),
                MainRoom = aRoom
            };

            var houses = new List<House>(new House[] { myHouse, yourHouse, donaldsHouse });

            // MainRoom.Name = \"a Room\" and Rooms.Count = 3 or 
            // ?????????????????????????
            var aRoomsHouses = houses.AsQueryable<House>().Where("MainRoom.Type = \"RoomType.Kitchen\"");

            Console.WriteLine("aRoomsHouses count = {0}", aRoomsHouses.Count());
            Console.ReadKey();
        }
    }

    public class House
    {
        public string Address { get; set; }
        public double Area { get; set; }
        public Room MainRoom { get; set; }
        public List<Room> Rooms { get; set; }
    }

    public class Room
    {
        public double Area { get; set; }
        public string Name { get; set; }
        public RoomType Type { get; set; }
    }

    public enum RoomType
    {
        Kitchen,
        Bedroom,
        Library,
        Office
    }
}

Answer 1

This works:

houses.AsQueryable<House>()
    .Where("MainRoom.Type = ConsoleApplication2.RoomType.Kitchen")

Answer 2

I encountered this same issue and tried the marked answer specified by @Steve Wilkes but it didn't work for me !! Then I discovered that dynamic LINQ has an HTML documentation in the same package which mentioned that Enums can be specified as String Literals.

houses.AsQueryable<House>().Where("MainRoom.Type = \"Kitchen\"")

Which worked for me.

Answer 3

This should work

houses.AsQueryable<House>().Where(rs=>rs.MainRoom.Type == RoomType.Kitchen);

Why do you need dynamic linq in this case? What output you expect

To my preference, use of error prone string should be avoided. If your class or property name changed, you won't be able to find the error until you encounter it.

Rather use expression

    Expression<Func<House, bool>> 
        filter = (p) => p.MainRoom.Type == RoomType.Kitchen; 
        filter = (p) => p.MainRoom.Area > 200;
        filter = (p) => p.Rooms.Sum(rs => rs.Area) > 500;
        filter = (p) => p.Address.Contains("abc");
        filter = (p) => p.Area > 200;
        ...
    var aRoomsHouses = houses.AsQueryable<House>().Where(filter);

You can create the expression where you decide which string filter to be used. Better create a static class or may be switch statement which gives you different type of expression which you can use as where argument.

Answer 4

in addition yet another variant use parameter

var aRoomsHouses = houses.AsQueryable<House>().Where("MainRoom.Type = @0",RoomType.Kitchen);

Answer 5

To add a new Enum type to dynamic linq, you must add the following code :

typeof(Enum),
typeof(T)

T : Enum type

in predefinedTypes of dynamic That's work for me;