using System;

using System.Linq;

using System.Collections.Generic;

public class Program

{

    public static void Main()

    {

        var file1 = new [] 

        {

            "line 1",

            "LiNe 2",

            "LINE 3",

            "Line 4"            

        };

        var file2 = new [] 

        {

            "line 1",

            "LiNe 2",

            "LINE 3",

            "Line 4"    

        };

        var file3 = new [] 

        {

            "foo",

            "LiNe 2",

            "LINE 3",

            "Line 4"

        };

        var file4 = new [] 

        {

            "wrong",

            "nope",

            "no"

        };

        //File1 and File2 are the same at 0 offset

        Console.WriteLine(FileCompareV2(file1, file2));

        //File1 and File3 are the same with an offset of 1

        Console.WriteLine(FileCompareV2(file1, file3, 1));

        //File1 and File4 are not at all the same

        Console.WriteLine(FileCompareV2(file1, file4));

    }

    //Version 1

    private static bool FileCompare(IEnumerable<string> file1, IEnumerable<string> file2, int offset = 0)

    {

        if(offset > 0)

        {

            file1 = file1.Skip(offset);

            file2 = file2.Skip(offset);

        }

        //gets two collections of the differences, ignoring case

        var firstNotSecond = file1.Except(file2, StringComparer.OrdinalIgnoreCase);

        var secondNotFirst = file2.Except(file1, StringComparer.OrdinalIgnoreCase);

        //If there is nothing in both collections they are the same

        return !firstNotSecond.Any() && !secondNotFirst.Any();

    }

    //Version 2

    private static bool FileCompareV2(IEnumerable<string> file1, IEnumerable<string> file2, int offset = 0)

    {

        if(offset > 0)

        {

            file1 = file1.Skip(offset);

            file2 = file2.Skip(offset);

        }

        return file1.SequenceEqual(file2, StringComparer.OrdinalIgnoreCase) && 

               file2.SequenceEqual(file1, StringComparer.OrdinalIgnoreCase);

    }

}

​

​