Create database connection

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Configuration;
using System.Data.SqlClient;
using System.Data;

namespace DalLibrary
{
    class DBConn
    {
        private static SqlConnection conn;
        private DBConn()
        {
        }
        /// <summary>
        /// get database connection
        /// </summary>
        /// <returns></returns>
        public static SqlConnection GetDbConnection()
        {
            try
            {
                if (conn == null)
                {
                    conn = new SqlConnection(ConfigurationManager.ConnectionStrings["PhoneConString"].ToString());
                    conn.Open();
                }
                else if (conn.State == ConnectionState.Closed)
                {
                    conn.Open();
                }
            }
            catch (Exception)
            {
               
                throw;
            }
        

            return conn;
        }
    }
}