Rolling Back Transaction After .Commit() Runs Successfully

I have a page that runs a transaction correctly after a button click.

I want to allow someone to click a button that rolls back the transaction, after the transaction runs on the first button click.

I can also successfully roll back within the first button click.

 I'm getting a NullReference error when trying to access SqlTransaction.Rollback() outside the button click.

 If SqlTransaction.Commit() completes without error can SqlTransaction.Rollback() be called after?

I tried making 'trans' a more global variable and it still gave me the error.

Button Click 1:

Dim trans As SqlTransaction

trans = connection.BeginTransaction()

try

'run SQL Statement

trans.Commit()

Catch e As Exception

 trans.Rollback()

throw e

end try

 

Button Click 2:

trans.Rollback()