I am struggling to implement SQL Membership provider and connection strings

<appsettings>
    <!-- [DATABSE SERVER SETTINGS}-->
    <add key="DB_Server" value="Enk-sql01.swh.mweb.co.za" />
    <add key="DB_User" value="Your Username" />
    <add key="DB_Pass" value="Your Password" />
    <add key="DB_Name" value="AspNetSql" />    
  </appsettings>

string ConnectionString = String.Format(@"Data Source = {0};User Id={1}; password={2}; Initial Catalog = {3};",
                            ConfigurationManager.AppSettings["DB_Server"],
                            ConfigurationManager.AppSettings["DB_User"],
                            ConfigurationManager.AppSettings["DB_Pass"],
                            ConfigurationManager.AppSettings["DB_Name"]);

string query = "your query here";

SqlConnection connection = new SqlConnection(ConnectionString);
connection.Open();
SqlCommand queryCMD = new SqlCommand(query, connection);
SqlDataReader queryReader = queryCMD.ExecuteReader();
while (queryReader.Read())
{
//do your work here
}