Connect database through config file

Question

Hi,

I want to connect database through configaration file. I am getting error. 

Here is my code:
Configuration file:

<?xml version="1.0" encoding="utf-8" ?>

<configuration>

  <connectionStrings>

    <add name="databaseconnectionstring" connectionString="i wrote connection string here"/>

    </connectionStrings> 

</configuration>


My code in c# is:



string connStr = ConfigurationManager.ConnectionStrings["databaseconnectionstring"].ConnectionString;
SqlConnection con = new SqlConnection(connStr);
con.open();


Thanks

Darma