Get ConnectionString from app.config

Question

I'm pretty sure there's some quick and easy error in this code but somehow I've spent the last 2 hours with this and couldn't solve it.

App.config:

<configuration>
  <connectionStrings>
    <add name="BO"
        connectionString="Data Source=MyServer;Initial Catalog=BO;User ID=WebUser;Password=MyPasswd"
        providerName="System.Data.SqlClient" />
  </connectionStrings>
</configuration>

Class.cs:

string connectionString = getNewConnection();
using (SqlConnection conn = new SqlConnection(connectionString)) { code }

Method.

public static string getNewConnection()
{
   return ConfigurationManager.ConnectionStrings["BO"].ConnectionString;
 }

Error:

Object reference not set to an instance of an object

on the line :

return ConfigurationManager.ConnectionStrings["BO"].ConnectionString;

EDIT:

Error image, the Spanish sentence means: Object reference not set to an instance of an object

Andrew Hagner · Accepted Answer · 2012-06-21 13:52:47Z

10

It should be:

ConfigurationManager.ConnectionStrings["BO"].ConnectionString;

Edit:

You will need the corresponding libraries as well if you don't have them yet, as mentioned in the below answers I think its System.Configuration

So in full you should have:

public static string getNewConnection()
{
    return ConfigurationManager.ConnectionStrings["BO"].ConnectionString;
}

edited Jun 21, 2012 at 13:52

answered Jun 21, 2012 at 13:28

Andrew Hagner

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11 Comments

Andrew Hagner Over a year ago

Corrected the library, it is System.Configuration

Daniel Sh. Over a year ago

if I use "ConnectionStringSettingsCollection connections = ConfigurationManager.ConnectionStrings["BO"].ConnectionString;" I get the error "Cannot implicitly convert type 'string' to 'System.Configuration.ConnectionStringSettingsCollection'"

Andrew Hagner Over a year ago

You don't need to do that, in your getNewConnection() function simply have return ConfigurationManager.ConnectionStrings["BO"].ConnectionString;

Daniel Sh. Over a year ago

the same error pops up in that line. Weird, would my app.config be wrong?

Daniel Sh. Over a year ago

it's solved! the app.config was in the same project as the class.cs, but for testing purposes I had created a new one with a windows form containing a datagrid with a simple select * from table from the desired server. I had to put the app.config inside that one project. (the reference was made to the Class.cs project so I didn't think that could matter at all) but indeed it did matter... I knew it was something that silly. Thanks a lot for your patience and help.

|

Ali Vojdanian · Accepted Answer · 2012-06-21 13:29:45Z

2

Use these codes in the Class :

class Connection
    {
        public static string con
        {
            get
            {
                return System.Configuration.ConfigurationManager.ConnectionStrings["sql"].ConnectionString;
            }
        }
    }

answered Jun 21, 2012 at 13:29

Ali Vojdanian

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1 Comment

Daniel Sh. Over a year ago

it gives me the same error (now referencing to your line of code). Would my app.config be wrong?

etlds · Accepted Answer · 2012-06-21 13:28:50Z

1

Did you use the WebConfigurationManager?

string MyConnectionString = System.Web.Configuration.WebConfigurationManager.ConnectionStrings["BO"].ConnectionString;

answered Jun 21, 2012 at 13:28

etlds

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1 Comment

Daniel Sh. Over a year ago

it says System.Web does not containg .Configuration etc. (I have added using System.Web )

daszarrin · Accepted Answer · 2013-07-22 10:29:09Z

0

Add a reference to System.Configuration.dll, and you should be able to use the System.Configuration.ConfigurationManager.

answered Jul 22, 2013 at 10:29

daszarrin

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