using System;

using System.IO;

using System.Linq;

using System.Collections.Generic;

​

public class Program

{

    public static void Main()

    {

        Console.WriteLine(GetFilteredFileInfo("..", new[]{".txt", "env"}).First().FullName);

    }

​

    public static IEnumerable<FileInfo> GetFilteredFileInfo(string path, IEnumerable<string> patterns, SearchOption option = SearchOption.TopDirectoryOnly)

    {

        return new DirectoryInfo(path).EnumerateFiles().Where(f => patterns.Any(ext => f.Name.ToLower().EndsWith(ext)));

    }

}