IOException while opening Bluetooth Serial Port of HC-06 module in Visual Studio (C#) -

i'm trying send input data arduino pc bluetooth serial connection using hc-06 module. while opening corresponding serial port, returns ioexception, means

the port in invalid state

but there aren't problems while connecting using serial monitor applications of windows , android (bt serial terminal)

after pairing bluetooth module, shows 2 com ports connected it:

1. com6 outgoing hc-06
2. com7 incoming hc-06 'dev b'

i suspected i'm using wrong port, tried both of them: first 1 opens, doesn't acquire data. second 1 gives ioexception while opening mentioned above , port said 1 needed used forums.

which com port should use actually? can cause problem it?

here list of bluetooth com ports:

visual studio code in c#

using system; using system.collections.generic; using system.componentmodel; using system.data; using system.drawing; using system.linq; using system.text; using system.threading.tasks; using system.windows.forms; using system.io; using system.io.ports; using system.threading;  namespace windowsformsapplication1 {     public partial class form1 : form     {             private static string buffer;          public form1()         {             initializecomponent();                  try             {                 serialport1.open();             }             catch (unauthorizedaccessexception) { console.writeline("error opening serial port"); }             catch (system.io.ioexception) { console.writeline("ioexception"); }              serialport1.datareceived += new serialdatareceivedeventhandler(readbuffer);             }          private void readbuffer(object sender, serialdatareceivedeventargs e)         {             this.invoke(new action(() =>             {                 buffer = string.empty;                 buffer = serialport1.readline();                 console.writeline(buffer);                /* if (buffer[0] == '@')                 {                     string c = string.empty;                     c += buffer[1];                     if (c == "%")                         sendkeys.send("{backspace}");                     else                         sendkeys.send(c);                 }*/              }));         }          private void initializecomponent()         {             this.components = new system.componentmodel.container();             this.textbox3 = new system.windows.forms.textbox();             this.serialport1 = new system.io.ports.serialport(this.components);             this.button1 = new system.windows.forms.button();             this.suspendlayout();             //              // textbox3             //              this.textbox3.location = new system.drawing.point(279, 296);             this.textbox3.multiline = true;             this.textbox3.name = "textbox3";             this.textbox3.size = new system.drawing.size(378, 147);             this.textbox3.tabindex = 2;             //              // serialport1             //              this.serialport1.portname = "com6";             //              // button1             //              this.button1.location = new system.drawing.point(329, 110);             this.button1.name = "button1";             this.button1.size = new system.drawing.size(283, 69);             this.button1.tabindex = 3;             this.button1.text = "led";             this.button1.usevisualstylebackcolor = true;             this.button1.click += new system.eventhandler(this.button1_click);             //              // form1             //              this.clientsize = new system.drawing.size(948, 549);             this.controls.add(this.button1);             this.controls.add(this.textbox3);             this.name = "form1";             this.resumelayout(false);             this.performlayout();             }          private void button1_click(object sender, eventargs e)         {             serialport1.write("1");         }     } } 

part of arduino code:

#define analog a0 #define rx 0 #define tx 1  void setup() {     serial.begin (9600);     pinmode (rx,input);     pinmode (tx,output); }  ...  int r = analogread(analog);     serial.println(r);