字符串防攻击，匿名函数

Posted 2020-08-21 吴皓杰

字符串攻击样式：

主要利用获取需用户输入的字符串时，通过输入精心编制的含有某种指令的字符串，从而对数据库进行攻击性操作。

\';(内容);--

那我们如何来防止攻击：主要是用Parameters这个集合

                    cmd.CommandText = "update Users set PassWord=@pwd,NickName=@nick,Sex=@sex,Birthday=@bir,Nation=@nation,Class=@cla where UserName=@uname";
                    cmd.Parameters.Clear();
                    cmd.Parameters.AddWithValue("@pwd", pwd);
                    cmd.Parameters.AddWithValue("@nick", nick);
                    cmd.Parameters.AddWithValue("@sex", sex);
                    cmd.Parameters.AddWithValue("@bir", bir);
                    cmd.Parameters.AddWithValue("@nation", nation);
                    cmd.Parameters.AddWithValue("@cla", cla);
                    cmd.Parameters.AddWithValue("@uname", uname);

                    conn.Open();
                    cmd.ExecuteNonQuery();
                    conn.Close();

通过使用此占位符来进行防字符串攻击，这样，占位符所代表的的仅仅是字符串，不带有代码含义。

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程序分三层：界面层、业务逻辑层、数据访问层

比较规范的写程序方法，要把业务逻辑层和数据访问层分开，此时需要创建实体类和数据访问类

封装类：

 

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

namespace 实体类_数据访问类.App_Code
{
    public class Users
    {
        private int _Ids;

        /// <summary>
        /// ids
        /// </summary>
        public int Ids
        {
            get { return _Ids; }
            set { _Ids = value; }
        }
        private string _UserName;

        /// <summary>
        /// 用户名
        /// </summary>
        public string UserName
        {
            get { return _UserName; }
            set { _UserName = value; }
        }
        private string _PassWord;

        /// <summary>
        /// 密码
        /// </summary>
        public string PassWord
        {
            get { return _PassWord; }
            set { _PassWord = value; }
        }
        private string _NickName;

        /// <summary>
        /// 昵称
        /// </summary>
        public string NickName
        {
            get { return _NickName; }
            set { _NickName = value; }
        }
        private bool _Sex;

        /// <summary>
        /// 性别
        /// </summary>
        public bool Sex
        {
            get { return _Sex; }
            set { _Sex = value; }
        }
        private DateTime _Birthday;

        /// <summary>
        /// 生日
        /// </summary>
        public DateTime Birthday
        {
            get { return _Birthday; }
            set { _Birthday = value; }
        }
        private string _Nation;

        /// <summary>
        /// 民族
        /// </summary>
        public string Nation
        {
            get { return _Nation; }
            set { _Nation = value; }
        }
        private string _Class;

        /// <summary>
        /// 班级
        /// </summary>
        public string Class
        {
            get { return _Class; }
            set { _Class = value; }
        }



    }
}

 

创建以上类，代表一个用户的所有数据

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数据访问类：便于调用

 

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

namespace 实体类_数据访问类.App_Code
{
    public class UsersData
    {
        SqlConnection conn = null;
        SqlCommand cmd = null;

        public UsersData()
        {
            conn = new SqlConnection("server=.;database=Data0928;user=sa;pwd=123");
            cmd = conn.CreateCommand();
        }

        /// <summary>
        /// 将数据添加到Users表中，返回true说明添加成功
        /// </summary>
        /// <param name="u">要添加到数据表中的Users对象</param>
        /// <returns></returns>
        public bool Insert(Users u)
        {
            bool ok = false;
            int count = 0;

            cmd.CommandText = "insert into Users values(@a,@b,@c,@d,@e,@f,@g)";
            cmd.Parameters.Clear();
            cmd.Parameters.AddWithValue("@a", u.UserName);
            cmd.Parameters.AddWithValue("@b", u.PassWord);
            cmd.Parameters.AddWithValue("@c", u.NickName);
            cmd.Parameters.AddWithValue("@d", u.Sex);
            cmd.Parameters.AddWithValue("@e", u.Birthday);
            cmd.Parameters.AddWithValue("@f", u.Nation);
            cmd.Parameters.AddWithValue("@g", u.Class);

            try
            {
                conn.Open();
                count = cmd.ExecuteNonQuery();
            }
            catch { ok = false; }
            finally
            {
                conn.Close();
            }

            if (count > 0)
                ok = true;

            return ok;
        }

        public List<Users> Select()
        {
            List<Users> list = new List<Users>();

            cmd.CommandText = "select *from Users";
            conn.Open();
            SqlDataReader dr = cmd.ExecuteReader();
            if (dr.HasRows)
            {
                while (dr.Read())
                {
                    Users u = new Users();
                    u.Ids = Convert.ToInt32(dr["ids"]);
                    u.UserName = dr["UserName"].ToString();
                    u.PassWord = dr["PassWord"].ToString();
                    u.NickName = dr["NickName"].ToString();
                    u.Sex = Convert.ToBoolean(dr["Sex"]);
                    u.Birthday = Convert.ToDateTime(dr["Birthday"]);
                    u.Nation = dr["Nation"].ToString();
                    u.Class = dr["Class"].ToString();

                    list.Add(u);
                }
            }
            conn.Close();

            return list;
        }

        public bool Select(string username)
        {
            bool has = false;
            cmd.CommandText = "select *from Users where UserName = @a";
            cmd.Parameters.Clear();
            cmd.Parameters.Add("@a",username);

            conn.Open();
            SqlDataReader dr = cmd.ExecuteReader();
            if (dr.HasRows)
                has = true;

            conn.Close();
            return has;
        }

        public void Delete(string uname)
        {
            cmd.CommandText = "delete from Users where UserName = @a";
            cmd.Parameters.Clear();
            cmd.Parameters.Add("@a",uname);

            conn.Open();
            cmd.ExecuteNonQuery();

            conn.Close();
        }

    }
}

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1、一般约定，在项目里新建一个叫做App_Code的文件夹，将封装的类和数据访问类统一放在其中

2、一般实体类使用想要进行操作的数据库中的表名来命名，数据库访问类用此表的表名后面加上Data来命名

3、注意数据访问类开头格式

        SqlConnection conn = null;
        SqlCommand cmd = null;

        public UsersData()
        {
            conn = new SqlConnection("server=.;database=Data0928;user=sa;pwd=123");
            cmd = conn.CreateCommand();
        }

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4、匿名函数：

List<Users> ulist = new UsersData().Select();

直接使用UserData类中的Select方法（查询表中所有数据），并赋值给叫做ulist的泛型集合，从而比较简便的获取到所有数据，节省代码。起到少用内存的效果。