SQL sid to text, C#

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//Rextester.Program.Main is the entry point for your code. Don't change it.
//Compiler version 4.0.30319.17929 for Microsoft (R) .NET Framework 4.5

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text.RegularExpressions;
using System.Text;
using System.Runtime.Remoting.Metadata.W3cXsd2001;

namespace Rextester
{
    public class Program
    {
        
        public static string ConvertByteToStringSid(Byte[] sidBytes)
        {
        
            StringBuilder strSid = new StringBuilder();
            strSid.Append("S-");
        
            // Add SID revision.
            strSid.Append(sidBytes[0].ToString());
            // Next six bytes are SID authority value.
            if (sidBytes[6] != 0 || sidBytes[5] != 0)
            {
                string strAuth = String.Format
                ("0x{0:2x}{1:2x}{2:2x}{3:2x}{4:2x}{5:2x}",
                (Int16)sidBytes[1],
                (Int16)sidBytes[2],
                (Int16)sidBytes[3],
                (Int16)sidBytes[4],
                (Int16)sidBytes[5],
                (Int16)sidBytes[6]);
                strSid.Append("-");
                strSid.Append(strAuth);
            }
            else
            {
                Int64 iVal = (Int32)(sidBytes[1]) +
                (Int32)(sidBytes[2] << 8) +
                (Int32)(sidBytes[3] << 16) +
                (Int32)(sidBytes[4] << 24);
                strSid.Append("-");
                strSid.Append(iVal.ToString());
            }
            
            // Get sub authority count...
            int iSubCount = Convert.ToInt32(sidBytes[7]);
            int idxAuth = 0;
            for (int i = 0; i < iSubCount; i++)
            {
                idxAuth = 8 + i * 4;
                
                if (idxAuth >= sidBytes.Length)
                {
                    Console.WriteLine("OK :old NT account");
                    return strSid.ToString();
                }
                
                UInt32 iSubAuth = BitConverter.ToUInt32(sidBytes, idxAuth);
                strSid.Append("-");
                strSid.Append(iSubAuth.ToString());
            }
            return strSid.ToString();
        } 
        
        public static void Main(string[] args)
        {
            //Your code goes here
            Console.WriteLine(
                ConvertByteToStringSid(
                    SoapHexBinary.Parse(
                        "0x01050000000000051500000079542007311FAE6D096510145E540300".Substring(2)
                    ).Value
                )
            );
        }
    }
}

Show compiler warnings [ + ] Show input
Compilation time: 0,12 sec, absolute running time: 0,08 sec, cpu time: 0,06 sec, average memory usage: 13 Mb, average nr of threads: 3