public static string IssueTransactionReferenceNumber()
{
var reference = new StringBuilder();
do
{
reference.Append(Convert.ToBase64String(Guid.NewGuid().ToByteArray()));
foreach (var disallowedChar in DisallowedChars)
{
reference.Replace(disallowedChar, string.Empty);
}
} while (reference.Length < 8);
return reference.ToString().Substring(0, 7);
}
}