18位流水号：

public static string GenerateTransId(int i)        {            string transId = DateTime.Now.ToString("yyyyMMddHHmmss");            int l = i - 14;            return transId + CreateRandCode(l);        }        public static string CreateRandCode(int codeLen)        {            string codeSerial = "1,2,3,4,5,6,7,a,c,d,e,f,h,i,j,k,m,n,p,r,s,t,A,C,D,E,F,G,H,J,K,M,N,P,Q,R,S,U,V,W,X,Y,Z";            if (codeLen == 0)            {                codeLen = 16;            }            string[] arr = codeSerial.Split(',');            string code = "";            int randValue = -1;            Random rand = new Random(unchecked((int)DateTime.Now.Ticks));            for (int i = 0; i < codeLen; i++)            {                randValue = rand.Next(0, arr.Length - 1);                code += arr[randValue];            }            return code;        }