ERROR:Object reference not set to an instance of an object.

Question

0.00/5 (No votes)

See more:

ERROR:System.NullReferenceException:Object reference not set to an instance of an object.

unhandled exception occurred during the execution of the current webpart.

CODE:

C#

using System;
using System.Configuration;
using System.Data;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.HtmlControls;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Xml.Linq;
using System.Data.SqlClient;


public partial class Default2 : System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs e)
    {

    }
    SqlConnection con = new SqlConnection("Data Source=.TEKPC26\\SQLEXPRESS;Initial Catalog=registration;Integrated Security=True");
    SqlCommand cmd;
    protected void Button1_Click(object sender, EventArgs e)
    {
        SqlConnection con = new SqlConnection(ConfigurationManager.ConnectionStrings["ApplicationServices"].ToString());
        con.Open();
        cmd = new SqlCommand("insert into values('" + TextBox1.Text + "','" + TextBox2.Text + "','" + TextBox3.Text + "')", con);
        cmd.ExecuteNonQuery();
    }
}

WEB.CONFIG CODE:

XML

<connectionStrings>
    <add name="registration" connectionString="data source=.TEKPC26\\SQLEXPRESS;Integrated Security=SSPI;AttachDBFilename=registration.mdf;User Instance=true" providerName="System.Data.SqlClient"/>
  </connectionStrings>

when execute my program getting one error!! is there any changes in web.config file?

Posted 6-Nov-11 22:49pm

muralikrishna53

Updated 6-Nov-11 23:13pm

v4

Add a Solution

Comments

thatraja 7-Nov-11 5:22am

Check my updated answer

[no name] 7-Nov-11 5:41am

i was changed my code with your advice, but one error..
<connectionstrings>
<add name="registration" connectionstring="data source=.TEKPC26\\SQLEXPRESS;Integrated Security=SSPI;AttachDBFilename=registration.mdf;User Instance=true" providername="System.Data.SqlClient">

"Unrecognized configuration section connectionstrings"

thatraja 7-Nov-11 7:29am

Check my updated answer again. Easy fix there at last. Let me know if still you are facing any issue.

3 solutions

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)

thatraja · Answer 1 · 2011-11-06T22:51:00

Debug your code & find out which line contains the issue

What does Object reference not set to an instance of an object mean[^]

EDIT
-------------------------------
Try this code

C#

public partial class Default2 : System.Web.UI.Page
{
    SqlConnection con;
    SqlCommand cmd;

    protected void Page_Load(object sender, EventArgs e)
    {
 
    }
    protected void Button1_Click(object sender, EventArgs e)
    {
        SqlConnection con = new SqlConnection(ConfigurationManager.ConnectionStrings["registration"].ToString());
        con.Open();
        cmd = new SqlCommand("insert into values('" + TextBox1.Text + "','" + TextBox2.Text + "','" + TextBox3.Text + "')", con);
        cmd.ExecuteNonQuery();
    }
}

HTML

<connectionstrings>
    <add name="registration" connectionstring="data source=.TEKPC26\\SQLEXPRESS;Integrated Security=SSPI;AttachDBFilename=registration.mdf;User Instance=true" providername="System.Data.SqlClient" />
  </connectionstrings>

BTW avoid Sql injection attacks
SQL injection
SQL Injection Attacks and Some Tips on How to Prevent Them[^]
SQL injection attacks[^]
SQL Injection Knowhow[^]
SQL Injection and Cross-Site Scripting[^]

EDIT 2
-------------------------------------

muralikrishna53 wrote:
i was changed my code with your advice, but one error..

"Unrecognized configuration section connectionstrings"

Here an easy fix
Error Solution: Fix for ‘Unrecognized configuration section connectionStrings’ Error in ASP.NET 2.0[^]

sravani.v · Answer 2 · 2011-11-06T22:54:00

Solution 2

No need of following code

SqlConnection con = new SqlConnection("Data Source=.TEKPC26\\SQLEXPRESS;Initial Catalog=registration;Integrated Security=True");

Replace "ApplicationServices" with "registration" like below

SqlConnection con = new SqlConnection(ConfigurationManager.ConnectionStrings["registration"].ToString());

Posted 6-Nov-11 22:54pm

sravani.v

Updated 6-Nov-11 22:55pm

v2

Comments

[no name] 7-Nov-11 4:55am

i just replaced your code but again showing same error!!

[no name] 7-Nov-11 4:58am

I just replaced your code, when executing the program getting one error! like..

ERROR:sqlexception was unhandled by user code.

"A network related or instance-specific error occurred while establishing a connection to sql server.the server was not found or was not accessible. Verify that the instance name is correct and that sql server is configured to allow remote connections."

P.Salini 7-Nov-11 5:22am

It means either Your connection string is wrong or you dont have permission to access that database server.

[no name] 7-Nov-11 6:36am

how to write connection strings related my code?

P.Salini · Answer 3 · 2011-11-06T22:54:00

Solution 3

In web.config you have give name of connection string as registration

so while accessing use that name

use this

C#

SqlConnection con = new SqlConnection(ConfigurationManager.ConnectionStrings["registration"].ToString());

Posted 6-Nov-11 22:54pm

P.Salini

Updated 6-Nov-11 22:55pm

v2

Comments

P.Salini 7-Nov-11 5:23am

It means either Your connection string is wrong or you dont have permission to access that database server.

[no name] 7-Nov-11 5:36am

i have permission, i was doing in administrator account. can u suggest how to write connection string code!!!

ERROR:Object reference not set to an instance of an object.

3 solutions

Solution 1

Solution 2

Solution 3

Add your solution here

Preview 0

Existing Members

...or Join us