# Wednesday, May 30, 2012


In .NET applications, Connection Strings are easily stored in and retrieved from a web.config file or an app.config file. Add a <connectionStrings> section to the config file, directly within the <configuration> section. Within the <connectionStrings> section, place an <add> tag for each connection string you wish to store and retrieve. This <add> tag contains two important attributes: name and connectionString. The name attribute will be used to look up an entry, so each <add> tag should have a unique name. The connectionString attribute contains the connection string you will use to connect to a database. If your application needs to connect to a number of different data types, it is worth setting the Provider property as well. This is the name of a database provider installed on the current machine, that will allow you to connect to a database.
An example is shown below:

    <add name="MyApp_Dev" 
        connectionString="Data Source=Server01;Initial Catalog=AwesomeDB_Dev;Integrated Security=True"/> <add name="MyApp_QA"
        connectionString="Data Source=Server01;Initial Catalog=AwesomeDB_QA;Integrated Security=True"/> <add name="MyApp_Prod"
        connectionString="Data Source=Server01;Initial Catalog=AwesomeDB;Integrated Security=True"/> </connectionStrings> </configuration>

To retrieve a connection string by its associated name attribute, use the utilities found in the System.Configuration namespace of the System.Configuration assembly. First, set a reference to System.Assembly by selecting the menu option Project | Add Reference, selecting the System.Assembly in the Component Name column of the .NET tab of the Add Reference dialog; and, clicking the OK button. Then, add the following using statement to the top of your class file.

This namespace contains the static ConfigurationManager class, which exposes a number of methods for retrieving configuration information. ConfigurationManager.ConnectionStrings returns a collection containing all connection strings settings in the config file of the current assembly. Once we have this collection, we can retrieve a single item by specifying its name. Doing so returns a ConnectionStringSettings object that contains properties retrieved from a single <add> element of the config file. The important property is ConnectionString, which can be used with ADO.NET to connect to a database. Knowing the Provider property may also be useful if your application connects to different types of data.
Sample code is below.

ConnectionStringSettingsCollection cssCollection =
ConnectionStringSettings devCsSettings = cssCollection["MyApp_Dev"];
string devCs = devCsSettings.ConnectionString;