using System;

using System.Collections.Generic;

using System.Linq;

using System.Linq.Expressions;

public class Program

{

    public static void Main()

    {

        var service = new UserService();

        Console.WriteLine("Found {0} users online", service.Find((e, v) => e.Online == v, true).Count());

        Console.WriteLine("Found {0} users offline", service.Find((e, v) => e.Online == v, false).Count());

        Console.WriteLine("Found bates when count is 1: {0}", service.Find((e, v) => e.Name == v, "Bates").Count());

        Console.WriteLine("PropertyName: {0}", service.GetName(e => e.Name));       

        Console.WriteLine("PropertyName: {0}", service.GetName(e => e.Online));

    }

}

​

public abstract class ServiceBase<T>

{

    public abstract IEnumerable<T> Find<TValue>(Func<T, TValue, bool> predicate, TValue val);

    public string GetName<TType>(Expression<Func<T, TType>> exp)

    {

        var expression = (MemberExpression)exp.Body;

        return expression.Member.Name;

    }

}

​

public class UserService : ServiceBase<User>

{

    public override IEnumerable<User> Find<TValue>(Func<User, TValue, bool> predicate, TValue val)

    {

        return Enumerable.Range(0, 10).Select(e => new User { Online = e % 2 == 0, Name = e == 1 ? "Bates" : string.Empty }).Where(e => predicate(e, val));

    }

}

​

public class User

{

    public bool Online { get; set; }    

    public string Name { get; set; }

}