删除时，　如何提示无记录

Try
            Dim sqlstr As String = "delete from userinfo where 用户编号='" & TextBox7.Text & "'"
            Dim comm As SqlCommand = New SqlCommand(sqlstr, cn)
            comm.ExecuteNonQuery()
            MessageBox.Show("删除成功")
        Catch ex As Exception
            MessageBox.Show(ex.ToString, "SQL 异常错误!", _
                   MessageBoxButtons.OK, MessageBoxIcon.Error)

        End Try

问题：没有记录也会提示删除成功．

请高手帮我修改下，如果没有数据，要出现＂无记录＂提示框