请问我这个问题是为什么啊

补充如下：Private Sub SerialPort1_DataReceived(ByVal sender As Object, ByVal e As ) Handles SerialPort1.DataReceived
        Dim i As UInteger = 0
        Thread.Sleep(50)                   '根据字符数量及波特率计算延时  单位为ms
        '  intNum = 0
        intNum = SerialPort1.BytesToRead
        If intNum = 0 Then
            Return
        End If
        ReDim rc(intNum)
        For i = 0 To (intNum - 1)
            rc(i) = SerialPort1.ReadByte 'strRec=SerialPort1.ReadLine
        Next
        If intNum > 4 Then
            flag1 = 1 'StatusDefine.TwoEnum
            '  If SerialPort1.IsOpen Then SerialPort1.Close()
        End If
    End Sub