commandField in detailView control

Hey,

in the website I'm developing, I use a detailView control to view my records. I vreate a custom button to behave as the default Edit/new button of the control for transaction need during the insert or update operation.

When I press on my button, I get an error message saying that:
'Cannot insert null in the column columnName' . However, when I use the default I got no error messag.

I think that the problem is with the parameter collection of the insertCommand or updatecommand but I don't know how to fix the problem.

my code looks like this
vb Code:
open connection
begin transaction 
try
    new Logcommand 
    detailView1.Insert
    logcommand.execute non query
    commit transacation
catch
    echo error
    rollback transaction
finally
    close connection
end try