DataReceivedEventHandler is called more than once

[selimsl]

Hi,

I am using System.IO.Ports.SerialPort to communicate with a device. I sent a command to the device then it sends reply to this command. I get the reply from device using DataReceived event of the serialport object. But reply comes with two parts (not everytime but sometimes it comes with two parts). I mean for example reply message is: "0103020001ABDE" but DataReceived is called two times with a time interval. First "010302" comes and then "0001ABDE" comes. But in this situation my code ignore the second part. Below is my code

 Private InputBuffer As String = Nothing

Private Function ReceiveSerialData() As String
        '**************************************
        Dim strReturn As String = String.Empty
        '**************************************
        If objSerialPort.IsOpen = Boolean.FalseString Then
            Throw New Exception("55")
        End If
        '**************************************
        objTimer.Enabled = True
        Do While (InputBuffer = Nothing)
            Application.DoEvents()
        Loop
        '**************************************
        objTimer.Enabled = False
        strReturn = InputBuffer
        InputBuffer = Nothing
        '**************************************
        Dim strTemp As String = String.Empty
        For intTemp As Integer = 0 To strReturn.Length - 1
            strTemp &= Hex(Asc(strReturn.Substring(intTemp, 1))).PadLeft(2, "0")
        Next
        strReturn = strTemp
        '**************************************
        Return strReturn
    End Function

 Private Sub DataReceivedEventHandler(ByVal sender As Object, ByVal e As IO.Ports.SerialDataReceivedEventArgs)
        '**************************************
        Dim spTemp As SerialPort = CType(sender, SerialPort)
        Do While (spTemp.BytesToRead > 0)
            InputBuffer &= spTemp.ReadExisting()
        Loop
        '**************************************
    End Sub

I am waiting untill InputBuffer is not nothing, When I get the first part of the message, the program skip the second part.

Do While (InputBuffer = Nothing)
Application.DoEvents()
Loop

Does anyone can help me about it?

thanks in advance

 

[selimsl]

When I put a breakpoint at Do While and wait for a second,
everthing works fine. I think I need a wait function to wait on that position for a while.

 Do While (InputBuffer = Nothing)
            Application.DoEvents()
        Loop