connectionstring: object reference not set to an object instance

Question

I want to connect with a db with a connectionstring in an application config file but always get this error :

object reference not set to an object instance

In the first code line with the ConfigurationManger I have checked it several times but I do not think that I have made a mistake. Hope you can find something.

Code

string con = ConfigurationManager.ConnectionStrings["dbConnect"].ConnectionString;
            using (SqlConnection conn = new SqlConnection(con))
            {
                SqlDataAdapter adapter = new SqlDataAdapter("Select* From dsds m with (nolock) inner join asdas a with (nolock) on a.id = m.id where  test....., conn);
                ds = new DataTable(" ");
                adapter.Fill(ds);
                dataGridView1.DataSource = ds;

App.config

<?xml version="1.0" encoding="utf-8" ?>
<configuration>
<connectionStrings>
<add name="dbConnect"
     connectionString="Data Source=test;Initial Catalog=as;Integrated Security=True"
     providerName="System.Data.SqlClient" />
</connectionStrings>
</configuration>

Possible duplicate of What does "Object reference not set to an instance of an object" mean? — ViRuSTriNiTy
– ViRuSTriNiTy, Commented Aug 23, 2016 at 10:11

Community · Accepted Answer · 2017-05-23 11:55:09Z

2

string con = System.Configuration.ConfigurationManager.ConnectionStrings["dbConnect"].ConnectionString;

Edit:

As you have two app.config, you can either delete one, or if you want to control programatically which app.config to use, Refer How can I use several Application Configuration Files in one project?

edited May 23, 2017 at 11:55

CommunityBot

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answered Aug 23, 2016 at 10:31

Richa Garg

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6 Comments

Richa Garg Over a year ago

Have you referenced the System.Configuration dll in your project?

Richa Garg Over a year ago

Do you have multiple app.config files?

myworld Over a year ago

yes i have otherwise i would not have get this error

Richa Garg Over a year ago

Sorry. I could not get for which question it was Yes.

Richa Garg Over a year ago

Can you please verify if System.Configuration is present in the References folder of your project?

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