Hi

I have written query like:

dim str as string="true"

Dim cmd As New OleDb.OleDbCommand("Select max(Invoice_No) from Invoice where flag= '" & str & "'", cn)

 cn.Open
If IsDBNull(cmd.ExecuteScalar()) = True Then

This statment fires exception:"No value given for one or more required parameters."

when i fire this query directly from access,it runs successfully

what is actual problem,i don't understand

Thanks
monika