Base58 is case SENSITIVE alphanumeric ELIMINATING: 0 (zero), I (uppercase), O (uppercase), l (lowercase)

Base58.cs

/// <summary>
/// Base58 is case SENSITIVE alphanumeric ELIMINATING: 0 (zero) I (uppercase), O (upppercase), l (lowercase)
/// This reduction of characters eliminates the majority of human typoposition errors    
///  </summary>   
public class Base58
{
    private static readonly BaseN base58 = new BaseN("123456789ABCDEFGHJKLMNPQRSTUVWXYZabcdefghijkmnopqrstuvwxyz"); //base58
    
    public static string Encode(long @long) => base58.Encode(@long);

    public static long DecodeLong(string encoded, bool truncate = false) => base58.DecodeLong(encoded, truncate);

    public static string Encode(byte[] data) => base58.Encode(data);

    public static byte[] Decode(string encoded) => base58.Decode(encoded);        
}
        
/// <summary>
/// Inspired by https://gist.github.com/CodesInChaos/3175971
/// </summary>
public class BaseN
{
    public BaseN(string characterSet)
    {
        CharacterSet = characterSet;
        EncodedMaxLong = Encode(long.MaxValue);
    }
    
    public string CharacterSet { get; }
    public int Base => CharacterSet.Length;
    public char[] CharMap => CharacterSet.ToCharArray();
    public string EncodedMaxLong { get; }

    public  string Encode(long @long)
    {
        var array = BitConverter.GetBytes(@long);
        var encoded = Encode(array);
        return encoded;
    }

    public  long DecodeLong(string encoded, bool truncate = false)
    {
        if (encoded.Length > EncodedMaxLong.Length && false == truncate)
            throw new ArgumentException($"{encoded} exceeds long.MaxValue : {EncodedMaxLong} and will truncate." +
                                            "Set truncate parameter to true to allow");

        var decoded = Decode(encoded);
        var @long = BitConverter.ToInt64(decoded, 0);

        return @long;
    }

    public  string Encode(byte[] data)
    {
        // Decode byte[] to BigInteger
        var intData = data.Aggregate<byte, BigInteger>(0, (current, @byte) => current * 256 + @byte);

        // Encode BigInteger to Base58 string
        var result = "";
        while (intData > 0)
        {
            var remainder = (int)(intData % Base);
            intData /= Base;
            result = CharacterSet[remainder] + result;
        }

        // Append `1` for each leading 0 byte
        for (var i = 0; i < data.Length && data[i] == 0; i++)
        {
            result = '1' + result;
        }
        return result;
    }

    public  byte[] Decode(string encoded)
    {
        // Decode Base58 string to BigInteger 
        BigInteger intData = 0;
        for (var i = 0; i < encoded.Length; i++)
        {
            var digitValue = Array.BinarySearch(CharMap, encoded[i]);
            if (digitValue < 0)
                throw new FormatException(string.Format("Invalid Base58 character `{0}` at position {1}", encoded[i], i));
            intData = intData * Base + digitValue;
        }

        // Encode BigInteger to byte[]
        // Leading zero bytes get encoded as leading `1` characters
        var leadingZeroCount = encoded.TakeWhile(c => c == '1').Count();
        var leadingZeros = Enumerable.Repeat((byte)0, leadingZeroCount);
        var bytesWithoutLeadingZeros =
            intData.ToByteArray()
                .Reverse() // to big endian
                .SkipWhile(b => b == 0); //strip sign byte
        var result = leadingZeros.Concat(bytesWithoutLeadingZeros).ToArray();
        return result;
    }
}

Made it so that encoder can be configurable base