短GUID

/// <summary>
/// 根據GUID獲取16位的惟一字符串
/// </summary>
/// <param name=\"guid\"></param>
/// <returns></returns>
public static string GuidTo16String()
{
    long i = 1;
    foreach (byte b in Guid.NewGuid().ToByteArray())
        i *= ((int)b + 1);
    return string.Format("{0:x}", i - DateTime.Now.Ticks);
}
/// <summary>
/// 根據GUID獲取19位的惟一數字序列
/// </summary>
/// <returns></returns>
public static long GuidToLongID()
{
    byte[] buffer = Guid.NewGuid().ToByteArray();
    return BitConverter.ToInt64(buffer, 0);
}

/// <summary>
/// 生成22位惟一的數字 併發可用
/// </summary>
/// <returns></returns>
public static string GenerateUniqueID()
{
    System.Threading.Thread.Sleep(1); //保證yyyyMMddHHmmssffff惟一
    Random d = new Random(BitConverter.ToInt32(Guid.NewGuid().ToByteArray(), 0));
    string strUnique = DateTime.Now.ToString("yyyyMMddHHmmssffff") + d.Next(1000, 9999);
    return strUnique;
}