Visual Studio中访问SQL数据库的方法

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

namespace Northwind_MDF_Test
{
    class Program
    {
        static void Main(string[] args)
        {
            string strcon = "Data Source=.;Initial Catalog=Northwind;Integrated Security=true";
            //"Data Source=.;Initial Catalog=Northwind;uid=sa;Pwd=Daniel";
            //下面使用配置文件调用数据库链接及加密
            //string strConCFG = ConfigurationManager.ConnectionStrings["ConNorthwind"].ConnectionString;
            //Configuration config = ConfigurationManager.OpenExeConfiguration(ConfigurationUserLevel.None);
            //config.ConnectionStrings.SectionInformation.ProtectSection(null);
            //config.Save(ConfigurationSaveMode.Full);

            SqlConnection con = null;
            SqlCommand cmd = null;
            SqlDataReader sdr = null;
            try
            {
                using (con = new SqlConnection(strcon))
                {
                    cmd = con.CreateCommand();
                    cmd.CommandText = "select CompanyName from Customers";
                    con.Open();
                    try { sdr = cmd.ExecuteReader(); }
                    catch (Exception ex) { Console.WriteLine("错误原因：{0}", ex.Message); Console.ReadKey(); }
                    while (sdr.Read())
                    {
                        Console.WriteLine(sdr[0]);
                    }
                    Console.WriteLine(con.State);
                }
            }catch (Exception ex) 
            {
                Console.WriteLine(ex.Message);
            }
            finally
            {
               // sdr.Close();
               // con.Close();
            }
            Console.WriteLine(con.State);
            Console.ReadKey();

        }
    }
}