主题：求助 查询结果不存在提示

怎样判断查询结果不存在呢

Dim yddh As String = e.Form.controls("TextBox3").Text
    If yddh IsNot Nothing Then
        Dim filter As String = "号码 = '" & yddh & "'"
        Tables("档案").filter = (filter)
    End If

上述代码中如果想提示“未查找到相关结果' 的提示框 应该怎样做呢