insertion valeur dans une table avec id (auto increment)

 Try
            Dim datep As New Date
            Dim dater As New Date
            datep = txtdatep.Text
            dater = txtdater.Text
            Dim hp As String
            Dim hr As String
            hp = txtheurep.Text
            hr = txtheurer.Text
            sqlstr = "INSERT INTO location(prise_le,remise_le,h_prise,h_remise,serie,cin) VALUES ('" & datep & "','" & dater & "','" & hp & "','" & hr & "','" & serie.Text.Trim & "','" & cin.Text.Trim & "')"
            Con.Open()
            cmd = New SqlCommand(sqlstr, Con)
            cmd.ExecuteReader()
            Con.Close()

            MsgBox("Ajout avec succès", MsgBoxStyle.Information)
        Catch ex As Exception
            MsgBox("Ajout impossible : champs incorrects !!!", MsgBoxStyle.Critical)
        End Try

 sqlstr = "INSERT INTO location(id,prise_le,remise_le,h_prise,h_remise,serie,cin) VALUES (NULL,'" & datep & "','" & dater & "','" & hp & "','" & hr & "','" & serie.Text.Trim & "','" & cin.Text.Trim & "')"