NULL REFERENCE EXCEPTION WAS UNHANDLED

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I created an app.config file and put the datasource in there incase it changes in the near future and i keep getting the null reference exception was unhandled.

use the new keyword as an object instance

but i have already imported the using system.configuration

and yet still. i have tried to catch but it seems not to work

C#

public partial class LoginForm : Form
    {
        //Main mnFrm;
        SqlConnection sqlConn = new SqlConnection(ConfigurationManager.ConnectionStrings["DbConn"].ToString());//the exception is thrown on this line when I run the program
        
        SqlDataReader sdr;
        SqlCommand sqlCmd = new SqlCommand();

        public LoginForm(Main mnFrm)
        {
            //this.mnFrm = mnFrm;
            InitializeComponent();
        }

I would appreciate the help guys thanks in advance

Posted 25-Jun-13 19:08pm

JoelonJada

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MuhammadUSman1 26-Jun-13 1:48am

I added solution please check it.

4 solutions

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MuhammadUSman1 · Answer 1 · 2013-06-25T19:47:00

Solution 4

C#

qlConnection sqlConn = new SqlConnection(ConfigurationManager.ConnectionStrings["DbConn"].ToString());//the exception is thrown on this line when I run the program

in this line you write Key "DbConn" dose not exist in your config file are you write wrong spell there.

Posted 25-Jun-13 19:47pm

MuhammadUSman1

Comments

JoelonJada 26-Jun-13 1:57am

that is the variablename for the connectionstring in the app.config file for which ever database it is to connect to in future

MuhammadUSman1 26-Jun-13 2:01am

Please post your config file code here, or you make sure that the spell you using in Code "DbConn" is same in your config file

JoelonJada 26-Jun-13 4:37am

MuhammadUSman1 26-Jun-13 6:42am

What is this?

JoelonJada 26-Jun-13 7:47am

Sorry I can't seem to figure out the tag for posting codes here...if you do please show me how

MuhammadUSman1 27-Jun-13 0:23am

If problem didn't solved yet. then please Past code of your config file. with dummy data.

Tom Wauters · Answer 2 · 2013-06-25T19:19:00

Solution 3

You can add a settingsfile to your solution and set the connectionstring there.
Then you can acces the connectionstring from the settingfile.

C#

using (SqlConnection sett = new SqlConnection(Settings.Default.Setting))
          {
            sett.open();
           //your code here;
          }

Posted 25-Jun-13 19:19pm

Tom Wauters

Updated 25-Jun-13 19:21pm

v2

Comments

JoelonJada 26-Jun-13 1:46am

Should i state this sett ing file as a global variable. Because i get the message the setting does not exist in the current context

Tom Wauters 26-Jun-13 2:51am

If you specifie it with a name, type as connectionString,scope: Application, and value as the connectionstring you want to use, you can just acces it as setting.Default."theNameofYourConnectionString"

_Amy · Answer 3 · 2013-06-25T19:18:00

Solution 2

Please see : How to get Connection String from App.Config in c#[^].

Also check :
MSDN : Storing and Retrieving Connection Strings [^]
Configuring Connection String in App.Config File During Runtime For a C# Windows Application[^]

--Amit

Posted 25-Jun-13 19:18pm

_Amy

Updated 25-Jun-13 19:19pm

v2

Comments

JoelonJada 26-Jun-13 8:08am

Thank you very much for that article. I will ask questions later.

_Damian S_ · Answer 4 · 2013-06-25T19:10:00

Solution 1

Do you have a connection called "DbConn" in the ConnectionStrings section of your config file?

Posted 25-Jun-13 19:10pm

_Damian S_

Comments

JoelonJada 26-Jun-13 1:44am

yes please i do

CHill60 26-Jun-13 8:56am

If you need further clarification from the OP please use the "Have a question or Comment?" link, don't post questions as Solutions

_Damian S_ 26-Jun-13 19:45pm

It wasn't a search for clarification... I was pointing the OP in the likely direction of his error... I prefer to guide people towards the answer rather than simply handing it to them on a plate.