using System.Collections.Generic;

using System.Linq;

using System;

​

public class Test

{

    public static void Main()

    {

        var myList = new List<string>(new string[] { "thing1", "thing2", "thing3", "else1", "else2", "else3", "other1", "other2", "other3" });

        var mySimplifiedList = new List<string>();

        if (myList.Any(str => str.StartsWith("thing")))

             mySimplifiedList.Add("thing");

        Console.WriteLine(string.Join(Environment.NewLine, mySimplifiedList));

    }

​

}