SQL server connectivity using ConfigurationManager.ConnectionString

I am not able to use

String connectionString = ConfigurationManager.ConnectionStrings["DevBackup"].ConnectionString;

I am getting error 'The nam开发者_JS百科e 'ConfigurationManager' does not exist in the current context'

I have used namespaces

using System.Data.SqlClient;
using System.Data.Sql;

what should be done..?? Am I missing something..??

You need to add a reference to the System.Configuration assembly to your project, and then a using System.Configuration; statement to your app.

Do you also have System.Configuration in your namespaces?

For ASP.NET, System.Web.Configuration is the correct namespace to use:

using System.Web.Configuration;
String connectionString = WebConfigurationManager.ConnectionStrings["DevBackup"].ConnectionString;