Object reference not set to an instance of an object

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Hello,
I am trying to insert data from textbox to SQL DB table.
When I am clicking on update button, getting below error

Server Error in '/' Application.

C#

Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code. 

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

Source Error:

C#

Line 81:         protected void Button2_Click(object sender, EventArgs e)
Line 82:         {
Line 83:             SqlConnection con = new SqlConnection(System.Configuration.ConfigurationManager.ConnectionStrings["conn"].ToString());
Line 84:             try
Line 85:             {

C#

SqlConnection con = new SqlConnection(System.Configuration.ConfigurationManager.ConnectionStrings["conn"].ToString());
           try
           {
               string query = "insert into Master_Data(Track_Status,Track_MRBDIR, Track_MRBDIRVer,Track_IssueDescr,Track_SrlNo,Track_TOCDIR,Track_Checker,Track_CheckerSAPID,Track_Approver,Track_ApproverSAPID,Track_WP,Track_Material,Track_PriorityLvl,Track_CostCode,Track_MNQty,Track_ForecastD,Track_MRBStatus)values('" + DropDownList1.Text + "','" + TextBox3.Text + "','" + TextBox4.Text + "','" + TextBox5.Text + "','" + TextBox6.Text + "','" + TextBox7.Text + "','" + TextBox8.Text + "','" + TextBox12.Text + "','" + TextBox9.Text + "','" + TextBox13.Text + "','" + TextBox10.Text + "','" + TextBox11.Text + "','" + DropDownList2.Text + "','" + TextBox14.Text + "','" + TextBox16.Text + "','" + TextBox17.Text + "','" + DropDownList3.Text + "');";
               SqlDataAdapter da = new SqlDataAdapter(query, conn);
               conn.Open();
               da.SelectCommand.ExecuteNonQuery();
               conn.Close();
               Updatelbl.Visible = true;
           }
           catch
           {
               conn.Close();
               //lblmessage.text = "Error while saving data.";

           }
       }

need your expertise to get this issue down.

Thank You

Posted 12-Jan-16 21:46pm

Member 12256084

Updated 12-Jan-16 22:33pm

StM0n

v2

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StM0n 13-Jan-16 4:32am

Additional to my solution, you should never trust user-input... don't just insert the text from controls w/o checking/escaping them or use parameters.

3 solutions

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StM0n · Answer 1 · 2016-01-12T22:04:00

Solution 1

Are you aware of the fact, that your connection you're instantiate is called con and the one you're trying to use is called conn?

BTW: put your con.close into a finally...

Posted 12-Jan-16 22:04pm

StM0n

Comments

Afzaal Ahmad Zeeshan 13-Jan-16 4:09am

5ed; good catch!

But, I wonder where does that conn come from as it may be another instance of the connection. Otherwise, "conn" does not exist in current context may have been the error.

StM0n 13-Jan-16 4:30am

I also wondered that... but maybe you're right, that there's a variable somewhere hiding :)

Ashwin. Shetty · Answer 2 · 2016-01-12T22:09:00

Solution 2

Check the line number you are getting this error. In exception also check for inner exception. This error mostly surface when the variable / control is been used before they are instantiated

Posted 12-Jan-16 22:09pm

Ashwin. Shetty

Dj@y · Answer 3 · 2016-01-13T00:13:00

Solution 3

please replace conn --> with con

C#

SqlDataAdapter da = new SqlDataAdapter(query, con);
               con.Open();
               da.SelectCommand.ExecuteNonQuery();
               con.Close();

then it works

Posted 13-Jan-16 0:13am

Dj@y

Updated 13-Jan-16 0:15am

v2

Comments

Dj@y 13-Jan-16 6:19am

And one thing whenever you write wrong code it show compile error,
in your case it should be give compile time error.
for conn. variable