Read connection string from web.config

Question

How can I read a connection string from a web.config file into a public class contained within a class library?

I've tried:

WebConfigurationManager

ConfigurationManager

But these classes are not recognized within my class library.

Solution 1

Add System.Configuration as a reference.

For some bizarre reason it's not included by default.

Solution 2

You need to add a reference to System.Configuration and then use:

System.Configuration.ConfigurationManager.
    ConnectionStrings["connectionStringName"].ConnectionString;

Solution 3

C#

// Add a using directive at the top of your code file    
using System.Configuration;

// Within the code body set your variable    
string cs = ConfigurationManager.ConnectionStrings["connectionStringName"].ConnectionString;

VB

' Add an Imports statement at the top of your code file    
Imports System.Configuration

' Within the code body set your variable    
Dim cs as String = ConfigurationManager.ConnectionStrings("connectionStringName").ConnectionString

Solution 4

Add System.Configuration as a reference then:

 using System.Configuration;

 ...

 string conn = 
    ConfigurationManager.ConnectionStrings["ConnectionName"].ConnectionString;

Solution 5

I guess you need to add a reference to the System.Configuration assembly if that have not already been added.

Also, you may need to insert the following line at the top of your code file:

using System.Configuration;

View more solutions

Comments

[Charles Burns]

Those parentheses need to be brackets.

[Alaa]

@CharlesBurns,Thanks, I wrote in VB by mistake, in C# sure it should be ConfigurationManager.ConnectionStrings["SQLServer"].Connecti‌​onString

[Charles Burns]

Ahh, I didn't even realize that was VB. I thought it was a typo. In a way, my mistake too.

[AechoLiu]

MSDN, System.configuration. It needs System.Configuration.dll.

[Mishax]

"Add a reference at the top of your code file" => that's a using directive, not a reference!

[BJladu4]

In Web project is better to use WebConfigurationManager in System.Web.Configuration.

[Matt]

Addition: Besides the indexer that accepts the name of the connection string, it is also allowed to use integer indices - which is useful if you want to read all connection strings in a for loop (for (int i = 0; i < numOfConnections; i++) { var conn = ConfigurationManager.ConnectionStrings[i]; ... }) and make them selectable in a combobox. With var numOfConnections = ConfigurationManager.ConnectionStrings.Count; you can determine how many connection strings exist. In this example conn.Name contains the name of the connection.