Unique Id in asp.net

Hi, I want to generate a unique id.
In my table i have column like - 

I am using MYSQL database and i want code in C#

Category - "Test Category"
Name - "Name Test"
UniqueId - ?

no i want to generate unique id like - "T_N_000001" for first data and for second it will be increment.... like "T_N_000002"
but if category = "Category" and Name = "Name" then it should start from C_N_000001

like this i want.....

if my question is not clear please tell me.