Connectivity with databa in asp.net

   <connectionstrings>
 <add name="testConnectionString" connectionstring="Data Source=PC\SQLEXPRESS;Initial Catalog=test;Persist Security Info=True;User ID=sa;Password=123">
  providerName="System.Data.SqlClient" />
</add></connectionstrings>

 string conn =  ConfigurationManager.ConnectionStrings["testConnectionString"].ConnectionString;
        using (SqlConnection con = new SqlConnection(conn))
        {
            con.Open();
        }

or
   using (SqlConnection con = new SqlConnection(@"Data Source=PC\SQLEXPRESS;Initial Catalog=test;Persist Security Info=True;User ID=sa;Password=123"))
        {
            con.Open();
         }