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

class Program
{
    public class Foo
    {
        public string data { get; set; }
    }

    public class Bar : Foo
    {
    }

    static void Main(string[] args)
    {
        var bars = new List<Bar>();

        bars.Add(new Bar() { data = "hello" });
        bars.Add(new Bar() { data = "world" });

        var resultsA = GetFoos(bars, (b => b.data.StartsWith("h")));
        var resultsB = GetBars(bars, (b => b.data.StartsWith("h")));
    }

    static List<Foo> GetFoos(IEnumerable<Foo> fooList, Func<Foo, bool> criteria)
    {
        return fooList.Where(criteria).ToList();
    }

    static List<Bar> GetBars(IEnumerable<Bar> barList, Func<Bar, bool> criteria)
    {
        return barList.Where(criteria).ToList();
    }
}