NullReferenceException when attempting to retrieve a connection string

Question

When I try

var con = new SqlConnection(
                  ConfigurationManager
                  .ConnectionStrings["RegConnectionString"]
                  .ConnectionString);

I get the following error:

Error message-null reference exception object reference not set to an instance of an object

What is going wrong?

You connection string is probably not defined in web.config or is named something else. — Candide, Mar 09 '12 at 19:39
well looks like there is no connection string named `RegConnectionString` defined in your config file? — BrokenGlass, Mar 09 '12 at 19:39
(assuming this is what you want to know, since your 'question' doesn't have an actual question, just a line of code and an exception message, I think that) The ConfigurationManager doesn't seem to have found your connection string. — MilkyWayJoe, Mar 09 '12 at 19:41
google: "**connection string webconfig**" - you'll surely find the answer! — Alex, Mar 09 '12 at 19:43
Whatever happened to requiring that a question actually be asked? — Bob Horn, Mar 09 '12 at 19:45
@BobHorn: Good point. But then, that's why anyone can [edit] to improve. — , Mar 09 '12 at 20:20

David · Answer 1 · 2012-03-09T19:45:07.793

Check for a mis-spelled or missing Configuration setting.

99.99999% of the time this error happens on this line of code, the issue is that the SqlConnecton setting in the Web.Config (or app.config) is either missing or mis-spelled.

(Actually, in my experience it's 100% of the time, but you never know. There are exceptions to darn near everything.)

From here:

Connection string in .NET 3.5 (and above) config file

Do not use appsettings in web.config. Instead use the connectionStrings section in web.config.

<connectionStrings>
<add name="myConnectionString" connectionString="server=localhost;database=myDb;uid=myUser;password=myPass;" />
</connectionStrings>

use the ConfigurationSettings class. string connStr =

ConfigurationManager.ConnectionStrings["myConnectionString"].ConnectionString;

So YOUR web.config should contain

<add name="RegConnectionString" connectionString="server=localhost;database=myDb;uid=myUser;password=myPass;" />

Of course, you'll need to replace the server name, database name, username, password, etc...

score 3 · Answer 2 · answered Mar 09 '12 at 19:42

3

Web.config:

<?xml version="1.0" encoding="utf-8"?>
<configuration>
    <!-- snip -->
    <connectionStrings>
        <add name="RegConnectionString"
             connectionString="Put your connex string here drrr" />
</connectionStrings>

answered Mar 09 '12 at 19:42

1

This is one of those times when the **blink** tag would be very beneficial. – M.Babcock Mar 09 '12 at 19:43

jrummell · Answer 3 · 2012-03-09T19:44:13.293

You are probably missing the RegConnectionString connection string in your web.config.

Here's an example. See MSDN for more information.

<configuration>
<!-- Other configuration settings -->
 <connectionStrings>    
  <add name="RegConnectionString" 
       providerName="System.Data.SqlClient" 
       connectionString="server=.;database=NorthWind;Integrated Security=SSPI" />    
 </connectionStrings>    
<!-- Other configuration settings -->
</configuration>

NullReferenceException when attempting to retrieve a connection string

3 Answers3

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