Object reference not set to an instance of an object in GsmmComLibrary ?

Question

0.00/5 (No votes)

See more:

Hi guys ;

I m using gsmcomm library.And while trying to send sms after i open ComPort and connect , error occurs "Object reference not set to an instance of an object"

what can be reason for it ?

This is image :

http://img423.yukle.tc/images/7996sms_sistem.png[^]

you can download solution folder here and you can test : http://www.ebitech.net/smsTest.rar

If you don't want to download the code is listed below:

C#

public SmsSubmitPdu pdu;
   public GsmCommMain comm=null;
    protected void Page_Load(object sender, EventArgs e)
    {

       
    }
  



   
    protected void Wizard1_FinishButtonClick(object sender, WizardNavigationEventArgs e)
    {

    }
    protected void btnSend_Click(object sender, EventArgs e)
    {
        pdu = new SmsSubmitPdu("test", "05452756736");
        comm.Open();
        comm.SendMessage(pdu);
        comm.Close();

        Response.Write("mesaj gonderildi");

    }
    protected void btnConnect_Click1(object sender, EventArgs e)
    {
        comm = new GsmCommMain(int.Parse(txtPort.Text), 3600, 360);
        comm.Open();
        Response.Write("port baglandi");


    }

Posted 20-Aug-12 10:22am

beratxt

Updated 20-Aug-12 10:39am

Wes Aday

v3

Add a Solution

Comments

[no name] 20-Aug-12 16:39pm

[Edit] Removed screaming [/Edit]

2 solutions

Solution 1

As you're using Response.Write, I assume this is a web site. You should tag your questions properly. You should also read up on how ASP.NET works and perhaps learn to use a debugger. The error means what it says, and it is right. Even though you didn't tell us what line creates the error, it's obvious.

C#

comm = new GsmCommMain(int.Parse(txtPort.Text), 3600, 360);
        comm.Open();
        Response.Write("port baglandi");

This is well and good.

C#

pdu = new SmsSubmitPdu("test", "05452756736");
  comm.Open();
  comm.SendMessage(pdu);
  comm.Close();

  Response.Write("mesaj gonderildi");

Here, comm is null, because it's a new postback and the web is stateless, your page gets recreated on each postback and can't remember the variables you created last time. You need to not have a 'connect' step, the samples you're looking at, assume this is not a web app.

Posted 20-Aug-12 10:29am

Christian Graus

Add a Solution

Add your solution here

Treat my content as plain text, not as HTML

Preview 0

…

Existing Members

Sign in to your account

...or Join us

Download, Vote, Comment, Publish.

Your Email
Password
Forgot your password?

Your Email
This email is in use. Do you need your password?
Optional Password

I have read and agree to the Terms of Service and Privacy Policy
Please subscribe me to the CodeProject newsletters

When answering a question please:

Read the question carefully.
Understand that English isn't everyone's first language so be lenient of bad spelling and grammar.
If a question is poorly phrased then either ask for clarification, ignore it, or edit the question and fix the problem. Insults are not welcome.
Don't tell someone to read the manual. Chances are they have and don't get it. Provide an answer or move on to the next question.

Let's work to help developers, not make them feel stupid.

This content, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

I.explore.code · Accepted Answer · 2012-08-20T10:29:00

Solution 2

ASP.NET by default doesn't preserve the state of the variables defined at page level So when the first time you hit btnConnect, the comm object gets initialised but also postback happens and the page is re-rendered and the variables are reset i.e. to null so when you hit btnSend, comm object is null again and hence the "object reference not set to instance of object" error. It simply means that you are trying to use an object that hasn't been initialised. Your best bet is to move this object creation and sending functionality to a seperate business or operation layer project which will reside on server side as a dll and then you would be able to use it correctly.

hope this helps.

[EDIT:] or you can use ViewState or Session variables to store and preserve this comm object in between postbacks

Posted 20-Aug-12 10:29am

I.explore.code

Updated 20-Aug-12 10:32am

v2

Comments

beratxt 20-Aug-12 16:34pm

What is the corrected code ? Can you tell me exactly ? Please inform me .I want to use opened port in all page that i open.Do you suggest to use Session or Cookie for port value ?

I.explore.code 20-Aug-12 16:37pm

try doing something like this, it should work:

protected void btnConnect_Click1(object sender, EventArgs e)
{
comm = new GsmCommMain(int.Parse(txtPort.Text), 3600, 360);
comm.Open();
//store in session for later use
Session["Comm"] = comm;
Response.Write("port baglandi");
}

and here:
protected void btnSend_Click(object sender, EventArgs e)
{
pdu = new SmsSubmitPdu("test", "05452756736");
//re-populate the comm object from the session.
comm = Session["Comm"];
comm.SendMessage(pdu);
comm.Close();

Response.Write("mesaj gonderildi");
}
give it a go, it should work. I personally don't use Session variables much so i prefer moving all such functionalities in a separate class residing on server side and then using it from there. But for now, see if this works in your case.

beratxt 20-Aug-12 16:44pm

comm = Session["Comm"]; has a problem cant imlicitly convert to GsmComm... etc ?

I.explore.code 20-Aug-12 16:49pm

try typecasting it: comm = (GsmCommMain)Session["Comm"];

beratxt 20-Aug-12 16:52pm

Thanks gladiatron ! the problem has been solved :)

I.explore.code 20-Aug-12 16:54pm

No problem mate! It would be great if you can accept my solution as an answer if it solved your problem, helps build rep u see ;)