Reversing CRC64

I'm looking for a way to reverse a CRC64 checksum. I already have CRC32 reversing implementation, and it actually reverses the checksum to it's original value, if it's 32 Bits in length. I have simply nothing to create a CRC64 reverse implementation. I tried multiple times but failed to do so. It is completely beyond my ability, so I'm hoping someone can piece together an implementation in C#.

Here is the CRC32 reversing code in C# which is working:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace MYC
{

    public class Crc32Reverse
    {
        public const uint poly = 0xedb88320;
        public const uint startxor = 0xffffffff;

        static uint[] table = null;
        static uint[] revtable = null;

        public void FixChecksum(byte[] bytes, int length, int fixpos, uint wantcrc)
        {
            if (fixpos + 4 > length) return;

            uint crc = startxor;
            for (int i = 0; i < fixpos; i++)
            {
                crc = (crc >> 8) ^ table[(crc ^ bytes[i]) & 0xff];
            }

            Array.Copy(BitConverter.GetBytes(crc), 0, bytes, fixpos, 4);

            List<uint> list = new List<uint>();

            crc = wantcrc ^ startxor;
            for (int i = length - 1; i >= fixpos; i--)
            {

                uint param0 = crc >> (3 * 8);
                list.Add(param0);
                crc = (crc << 8) ^ revtable[param0] ^ bytes[i];
            }

            Array.Copy(BitConverter.GetBytes(crc), 0, bytes, fixpos, 4);
        }

        public Crc32Reverse()
        {
            if (Crc32Reverse.table == null)
            {
                uint[] table = new uint[256];
                uint[] revtable = new uint[256];

                uint fwd, rev;
                for (int i = 0; i < table.Length; i++)
                {
                    fwd = (uint)i;
                    rev = (uint)(i) << (3 * 8);
                    for (int j = 8; j > 0; j--)
                    {
                        if ((fwd & 1) == 1)
                        {
                            fwd = (uint)((fwd >> 1) ^ poly);
                        }
                        else
                        {
                            fwd >>= 1;
                        }

                        if ((rev & 0x80000000) != 0)
                        {
                            rev = ((rev ^ poly) << 1) | 1;
                        }
                        else
                        {
                            rev <<= 1;
                        }
                    }
                    table[i] = fwd;
                    revtable[i] = rev;
                }

                Crc32Reverse.table = table;
                Crc32Reverse.revtable = revtable;
            }
        }
    }
}

I have tried everything but I failed to create a CRC64 reverse code. It is beyond my ability.