C# 流水号序列号生成 [0,9]~[A,Z]

public class SerialNum
{
    public SerialNum()
    {
        m_NumByteArr = new byte[4] { 48, 48, 48, 48 };
        //m_NumByteArr = new byte[4] { 90, 90, 90, 90 };
        ExcludeChar = new List<byte>
        {
           (byte) 'A',
           (byte) 'E',
           (byte) 'I',
           (byte) 'O',
           (byte) 'U'
        };
    }

    public List<byte> ExcludeChar { get; }

    /**0~9  十进制ASCII码[48, 57] **/
    /**A~Z  十进制ASCII码[65, 90]**/
    public string Number
    {
        get
        {
            return Encoding.Default.GetString(m_NumByteArr);
        }
    }
    protected byte[] m_NumByteArr;

    public bool AddOne()
    {
        m_NumByteArr[3] = AddChar(m_NumByteArr[3]);
        if (m_NumByteArr[3] > (byte)'Z')
        {
            m_NumByteArr[2] = AddChar(m_NumByteArr[2]);
            m_NumByteArr[3] = (byte)'0';
        }
        if (m_NumByteArr[2] > (byte)'Z')
        {
            m_NumByteArr[1] = AddChar(m_NumByteArr[1]);
            m_NumByteArr[2] = (byte)'0';
        }
        if (m_NumByteArr[1] > (byte)'Z')
        {
            m_NumByteArr[0] = AddChar(m_NumByteArr[0]);
            m_NumByteArr[1] = (byte)'0';
        }

        return m_NumByteArr[0] <= (byte)'Z';
    }

    public bool SubOne()
    {
        m_NumByteArr[3] = SubChar(m_NumByteArr[3]);
        if (m_NumByteArr[3] < (byte)'0')
        {
            m_NumByteArr[2] = SubChar(m_NumByteArr[2]);
            m_NumByteArr[3] = (byte)'Z';
        }
        if (m_NumByteArr[2] < (byte)'0')
        {
            m_NumByteArr[1] = SubChar(m_NumByteArr[1]);
            m_NumByteArr[2] = (byte)'Z';
        }
        if (m_NumByteArr[1] < (byte)'0')
        {
            m_NumByteArr[0] = SubChar(m_NumByteArr[0]);
            m_NumByteArr[1] = (byte)'Z';
        }

        return m_NumByteArr[0] >= (byte)'0';
    }

    private byte AddChar(byte ch)
    {
        while (true)
        {
            ch++;
            if (!ExcludeChar.Contains(ch))
            {
                break;
            }
        }

        if (ch == ((byte)'9' + 1))
        {
            ch = (byte)'B';
        }
        return ch;
    }
    private byte SubChar(byte ch)
    {
        while (true)
        {
            ch--;
            if (!ExcludeChar.Contains(ch))
            {
                break;
            }
        }

        if (ch == ((byte)'A' - 1))
        {
            ch = (byte)'9';
        }

        return ch;
    }
}