Creating a unique id

private string GetRandomString()
       {
           Random rand = new Random((int)DateTime.Now.Ticks);
           int randomIndex1 = rand.Next(100, 999);
           int randomIndex2 = rand.Next(10000, 99999);
           string randstring = RandomString(3);

           string result = "#" + randstring + "-" + randomIndex1.ToString() + "-" + randomIndex2.ToString();
           return result;
       }

       private static Random random = new Random((int)DateTime.Now.Ticks);
       private string RandomString(int size)
       {
           StringBuilder builder = new StringBuilder();
           char ch;
           for (int i = 0; i < size; i++)
           {
               ch = Convert.ToChar(Convert.ToInt32(Math.Floor(26 * random.NextDouble() + 65)));
               builder.Append(ch);
           }

           return builder.ToString();
       }