How to insert NULL into database if form field is empty

Question

I have a form and stored procedure that inserts the data from the form. It works fine except that if a field isn\'t filled in it doesn\'t insert a NULL into SQL

Answer 1

If RdFree.Checked = True Then
    Dim nu As String = "NULL"
    UpdPolicys.Append(", AccIDFree = " & nu & " , AccTypeIDFree = " & nu & " ")
End If