NEED HELP-Showing the serial data more than 1 in visual studio

Using Arduino Project Guidance
1

I want to show 4 datas from different IR sensor from my arduino in Visual studio GUI, but it cant work properly, anyone can help me what should I do with my program? thanks.

(Pleas use Code Tags in future posts please!)

Here is my program for arduino:

const int sensorread = A0;
const int sensorread1 = A1;
const int sensorread2 = A2;
const int sensorread3 = A3;

void setup()
{
  Serial.begin(9600);
  pinMode(sensorread, INPUT);
  pinMode(sensorread1, INPUT);
  pinMode(sensorread2, INPUT);
  pinMode(sensorread3, INPUT);
  
}

void loop()
{
  int counter = 0;
  int counter1 = 0;
  int counter2 = 0;
  int counter3 = 0;
  
  byte state;
  byte state1;
  byte state2;
  byte state3;
  
  byte laststate;
  byte laststate1;
  byte laststate2;
  byte laststate3;
  
  laststate = digitalRead(sensorread);    // Pre-load last state
  laststate1 = digitalRead(sensorread1);
  laststate2 = digitalRead(sensorread2);
  laststate3 = digitalRead(sensorread3);
  Serial.println("Begin...");
  unsigned long startTime = millis();     // Get current chip time
  while((startTime + 30000) > millis())
  {
    state = digitalRead(sensorread);
     state1 = digitalRead(sensorread1);
      state2 = digitalRead(sensorread2);
       state3 = digitalRead(sensorread3);
    if (state != laststate)
    {
      counter++;                          // Increments twice per drop so divide by 2 to get true count
      laststate = state;
      delay (30);                         // Debounce
    }
    
     if (state1 != laststate1)
    {
      counter1++;                          // Increments twice per drop so divide by 2 to get true count
      laststate1 = state1;
      delay (30);                         // Debounce
    }
    
     if (state2 != laststate2)
    {
      counter2++;                          // Increments twice per drop so divide by 2 to get true count
      laststate2 = state2;
      delay (30);                         // Debounce
    }
    
     if (state3 != laststate3)
    {
      counter3++;                          // Increments twice per drop so divide by 2 to get true count
      laststate3 = state3;
      delay (30);                         // Debounce
    }
  }
  
 char on_sensor = 'n';
  if (Serial.available()>0)
  {
    on_sensor = Serial.read();
  }

  if (on_sensor == 'a')
  {
     Serial.println (counter/2);
  }

  if (on_sensor == 'b')
  {
    Serial.println (counter1/2);
  }
 
  if (on_sensor == 'c')
  {
     Serial.println (counter2/2);
  }

  if (on_sensor == 'd')
  {
    Serial.println (counter3/2);
  }
}

and here is my program in Visual studio 2010:

Imports System.IO
Imports System.IO.Ports
Imports System.Threading


Public Class Form1

    Dim i
    Dim i2
    Dim i3
    Dim i4

    Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
        SerialPort1.Close()
        SerialPort1.PortName = "com5"
        SerialPort1.BaudRate = 9600
        SerialPort1.DataBits = 8
        SerialPort1.Parity = Parity.None
        SerialPort1.StopBits = StopBits.One
        SerialPort1.Handshake = Handshake.None
        SerialPort1.Encoding = System.Text.Encoding.Default

        Timer1.Start()



    End Sub


    Private Sub Timer1_Tick(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Timer1.Tick

        SerialPort1.Open()
        SerialPort1.Write("a")
        System.Threading.Thread.Sleep(250)
        Dim i As Integer = SerialPort1.ReadLine()
        Label1.Text = i
        SerialPort1.Close()

        SerialPort1.Open()
        SerialPort1.Write("b")
        System.Threading.Thread.Sleep(250)
        Dim i2 As Integer = SerialPort1.ReadLine()
        Label2.Text = i2
        SerialPort1.Close()

SerialPort1.Open()
        SerialPort1.Write("c")
        System.Threading.Thread.Sleep(250)
        Dim i3 As Integer = SerialPort1.ReadLine()
        Label3.Text = i3
        SerialPort1.Close()

SerialPort1.Open()
        SerialPort1.Write("d")
        System.Threading.Thread.Sleep(250)
        Dim i4 As Integer = SerialPort1.ReadLine()
        Label4.Text = i4
        SerialPort1.Close()

    End Sub
End Class
2 
      counter++;                          // Increments twice per drop so divide by 2 to get true count

So your comments indicate that you know this line is being run twice for each 'true' count.

Do you know why you get two counts? Is it some feature of the sensor? When you say "more than 1" do you mean "exactly 2"?

In your VB code, you are opening and closing the serial port many times. This will probably reset the Arduino like it resets every time the serial monitor connects. Is this the problem?