web.config connection string in c# asp.net

Web.config

<?xml version="1.0"?>

<configuration>

  <connectionStrings>

    <add name="conString" connectionString="Data Source=NEERAJ-PC\Neeraj; Initial Catalog =registrationform ;User ID=sa; Password=12345678"/>

   

  </connectionStrings>

       <system.web>

              <compilation debug="true" targetFramework="4.0"/>

       </system.web>

</configuration>

C# code:-

String ConnString = ConfigurationManager.ConnectionStrings["conString"].ConnectionString;

        SqlConnection con = new SqlConnection(ConnString);

        SqlCommand cmd = new SqlCommand();