C#连接数据库，登录

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Data.SqlClient;

namespace Login
{
    class Program
    {
        static void Main(string[] args)
        {
            //数据库在debug和release下的处理
            string dataDir = AppDomain.CurrentDomain.BaseDirectory;
            if (dataDir.EndsWith(@"\bin\Debug\")
                || dataDir.EndsWith(@"\bin\Release\"))
            {
                dataDir = System.IO.Directory.GetParent(dataDir).Parent.Parent.FullName;
                AppDomain.CurrentDomain.SetData("DataDirectory", dataDir);
            }

            //登录提示
            Console.WriteLine("请输入用户名");
            string username = Console.ReadLine();
            Console.WriteLine("请输入密码");
            string password = Console.ReadLine();
            //数据库连接
            using (SqlConnection conn = new SqlConnection(@"Data Source=.\SQLEXPRESS;AttachDBFilename=|DataDirectory|\Database1.mdf;Integrated Security=True;User Instance=True"))
            {
                conn.Open();
                //Console.WriteLine("数据库连接成功！");
                /*
                //创建表
                using(SqlCommand cmd = conn.CreateCommand())
                {
                    //cmd.CommandText = "create table T_user(TId int not null,TUsername nvarchar(50),TPassword nvarchar(50),primary key(TId))";
                    cmd.ExecuteNonQuery();
                }*/
                using (SqlCommand cmd = conn.CreateCommand())
                {
                    cmd.CommandText = "select * from T_users where TUsername='"+username+"'";
                    using (SqlDataReader reader = cmd.ExecuteReader())
                    {
                        if(reader.Read()) //如果存在数据
                        {
                            string dbPassword = reader.GetString(reader.GetOrdinal("TPassword"));
                            if (dbPassword == password)
                            {
                                Console.WriteLine("登录成功");
                            }
                            else
                            {
                                Console.WriteLine("密码错误");
                            }
                        }
                        else    //如果不存在数据
                        {
                            Console.WriteLine("用户名错误");
                        }
                    }
                }

            }
           
            Console.ReadKey();
        }
    }
}