how i auto create invoice id

Question

how i auto generate invoice id /  how i auto generate Truncation id

(like):-

Name=Ram

Age=20

Address= Kolkata

Cash=5000

due=0

save click then truncation id / invoice id auto generate into lable box / Text box

truncation id=AG002 or  invoice id = DT1340M

invoice id = ZS1340M or truncation id=RK1462P

when due=0 then truncation id / invoice id auto generate when click save button.

this is only C# program _Project

Plz Help me , i am waiting for ur perfect & clear ans.

PLZ send me the sampal project which i see as soon as i understand .