C# syntax to Generate Sequence number with Prefix

Hi
  I want to generate an unique  15 digit sequence number with prefix.
eg: PT0000000000001 , PT0000000000002 , PT0000000000003..............PT0000000000015,................PT0000000000250
I will start from 1 and append the required prefix at the First 2 characters(PT). I want to append Zeros to make a 15 digit number.
I will store the last increment number in table and add 1 and store it again during next generation.
How to achieve this using C# syntax?
thanks
Ashok
 
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