How to use Appsettings values into our application

write code in web.config..........

<appSettings>
<add key="add" value="S R Nagar AmeerPet Hyderabad"/>
<add key="const" value="user id=sa;password=123;database=mydatabase;data source=."/>
</appSettings>





 protected void Page_Load(object sender, EventArgs e)
    {
        System.Data.SqlClient.SqlConnection cn = new System.Data.SqlClient.SqlConnection();
        Label2.Text=ConfigurationSettings.AppSettings["add"];
        cn.ConnectionString=ConfigurationSettings.AppSettings["const"];
    }