namespace Telenews.Db
{
    public class DBManager
    {
        private static SqlConnection conn = null;
        private static DBManager instance;
        private DBManager() { }

        public static DBManager Instance()
        {
            if (instance == null)
            {
                instance = new DBManager();
            }
            return instance;
        }
.......

private DBManager db = DBManager.Instance();