auto identity for each Type

Hello,

I am working on an accounting system using VB.NET and sql server 2005 as a database. the application should be used by multiple users.
i have a the following structure:
Voucher: ID (primary), Date,TypeID, ReferenceCode, ....
Type: ID, Code, Name. (the user can add new type anytime!)
(Ex: PV- payment voucher, JV - Journal Voucher ,...)

When adding a voucher the user will choose a type, according to this type (for each year) a counter will be increminted.
for example: PV1, PV2...PV233,... the other type will have its separate counter JV1, JV2 ,...JV4569,..
I am using the sqlTransaction cause i am doing other operations that should be transactional with the insertion of the Voucher.

The question is :
What is the best solution to generate a counter for each type?(With code sample)

Thanks.do you really need to have the 'PV' and 'JV' before each value? if you could use ints, then you could use identity columns. That's the standard way of doing this.

You can always tack on a JV or PV in the front end if that's the way your boss wants it to look in a report or something.

from BOL:

IDENTITY

Indicates that the new column is an identity column. When a new row is added to the table, Microsoft® SQL Server™ provides a unique, incremental value for the column. Identity columns are commonly used in conjunction with PRIMARY KEY constraints to serve as the unique row identifier for the table. The IDENTITY property can be assigned to tinyint, smallint, int, bigint, decimal(p,0), or numeric(p,0) columns. Only one identity column can be created per table. Bound defaults and DEFAULT constraints cannot be used with an identity column. You must specify both the seed and increment or neither. If neither is specified, the default is (1,1).|||if you were using mysql, this functionality (starting a new auto_increment within each type group) is built in

it's impossible to do this with an IDENTITY column

you will have to generate your own numbers, and i would recommend very strongly against it|||the counter in the question is the ReferenceCode in the Voucher table
Voucher: ID (primary), Date,TypeID, ReferenceCode.
so for each added voucher and according to the TypeID a the reference code will be generated. let say the last counter for the PV type is 230 so the referenceCode will be PV231. if the Type is JV and the last counter is 566 then the ReferenceCode will be JV567 and so on.
We don't have to forget that we are working in a multi user enviroment, and the Reference Code should be unique .|||put the JV or PV in another field and concatenate it in the front end. smart numbers are stupid and loved by the accounting types. this kind of things slow down joins and causes other kinds of pain. i have not seen smart numbers in a project for five years and that was a legacy foxpro app.