winform+mysql入門學習

　　畢業后，第一份工作是寫單片機(C)代碼的，這一份也是寫C代碼的(emmmmmmmmm,雖然入職兩個多月了一行代碼也沒寫過啊哈哈哈哈)，所以好久沒寫過博客了，周末沒事干(沒有女朋友，單身23年嗚嗚嗚嗚嗚)就學了下C#和MySQL，然后就寫了個最簡單的類似於“hello world”的小項目-圖書管理系統，這部分博文只有用戶管理部分的，這篇文章主要是記錄自己的學習過程。

　　C#沒什么好說的，只不過是一種面向對象編程語言，大學期間上課不認真聽講學習的，啊哈哈哈哈，MySQL是在bilibili看某智博客的視頻學的，都算是半路出家的，所以博文水平低，質量差大佬勿噴，當然這也是我自己學習的記錄，大佬可以細心指教，千恩萬謝。

　　首先說下C#的三層架構，如下這段話是從大佬的博客里面學習的：

　　三層架構分為：表現層（UI（User Interface））、業務邏輯層（BLL（Business Logic Layer））、數據訪問層（DAL（Data Access Layer））再加上實體類庫（Model）。實體類庫（Model），主要存放數據庫中的表字段；數據訪問層（DAL），主要是存放對數據類的訪問，即對數據庫的添加、刪除、修改、更新等基本操作；業務邏輯層（BLL）對傳送數據進行邏輯判斷分折，並進行傳送正確的值；表現層（UI）即用戶界面層。

　　如下圖所示，是我的工程文件結構，2_StudentForm是表示(UI)層，添加的是Windows窗體應用程序；StudentBLL是業務邏輯層，StudentDAL是數據訪問層，StudentModel是實體類庫，這三個均是類庫。

　　UI層沒什么好說的，我這種菜鳥還是喜歡拖控件，然后寫需要的事件就行。

　　Model層與數據庫字段表相對應，如下：

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

namespace StudentModel
{
    public class UserInfoModel
    {
        /// <summary>
        /// 用戶ID
        /// </summary>
        public int Id { get; set; }

        /// <summary>
        /// 用戶名
        /// </summary>
        public string Name { get; set; }

        /// <summary>
        /// 密碼
        /// </summary>
        public string Pwd { get; set; }
    }
}

　　DAL是數據庫操作的相關代碼，在DAL類庫中引用Model類庫，我就寫了最基礎的sql操作代碼，如下：

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using StudentModel;
using MySql.Data.MySqlClient;
using System.Data;

namespace StudentDAL
{
    public class UserInfoDAL
    {
        const string str = "server = localhost;user = root;password=1234;database = student";
        MySqlConnection conn = new MySqlConnection(str);

        /// <summary>
        /// 從數據庫查找用戶
        /// </summary>
        /// <param name="_userInfoModel"></param>
        /// <returns></returns>
        public UserInfoModel MySqlSelectUser(UserInfoModel _userInfoModel)
        {   
            conn.Open();
            string sqlstr = String.Format("select * from userinfo where name = '{0}' and pwd = '{1}'", _userInfoModel.Name, _userInfoModel.Pwd);
            MySqlCommand cmd = new MySqlCommand(sqlstr, conn);
            MySqlDataReader reader = cmd.ExecuteReader();
            UserInfoModel user = new UserInfoModel();

            if(reader.Read())
            {
               user.Id = reader.GetInt32(0);
               user.Name = reader.GetString(1);
               user.Pwd = reader.GetString(2);
            }

            conn.Close();
            return user;
        }

        /// <summary>
        /// 從數據庫查找用戶名
        /// </summary>
        /// <param name="_userInfoModel"></param>
        /// <returns></returns>
        public UserInfoModel MySqlSelectName(UserInfoModel _userInfoModel)
        {
            conn.Open();
            string sqlstr = String.Format("select * from userinfo where name = '{0}'", _userInfoModel.Name);
            MySqlCommand cmd = new MySqlCommand(sqlstr, conn);
            MySqlDataReader reader = cmd.ExecuteReader();
            UserInfoModel user = new UserInfoModel();

            if (reader.Read())
            {
                user.Id = reader.GetInt32(0);
                user.Name = reader.GetString(1);
                user.Pwd = reader.GetString(2);
            }

            conn.Close();
            return user;
        }

        /// <summary>
        /// 查詢所有數據
        /// </summary>
        /// <returns></returns>
        public List<UserInfoModel> MySqlSelectUserAll()
        {
            List<UserInfoModel> list = new List<UserInfoModel>();
            conn.Open();
            string sqlstr = "select * from userinfo";
            DataTable dt = new DataTable();
            MySqlDataAdapter rd = new MySqlDataAdapter(sqlstr, conn);
            rd.Fill(dt);

            foreach (DataRow dr in dt.Rows)
            {
                UserInfoModel ai = new UserInfoModel
                {
                    Id = Convert.ToInt32(dr["Id"]),
                    Name = dr["Name"].ToString(),
                    Pwd = dr["Pwd"].ToString()
                };
                list.Add(ai);
            }

            conn.Close();
            return list;
        }

        /// <summary>
        /// 刪除用戶
        /// </summary>
        /// <param name="_userInfoModel"></param>
        public int MySqlDelUser(UserInfoModel _userInfoModel)
        {
            conn.Open();
            string sqlstr = String.Format("delete from userinfo where name = '{0}'", _userInfoModel.Name);
            MySqlCommand cmd = new MySqlCommand(sqlstr, conn);
            int iRet = cmd.ExecuteNonQuery();
            conn.Close();
            return iRet;
        }

        /// <summary>
        /// 插入數據
        /// </summary>
        /// <param name="_userInfoModel"></param>
        /// <returns></returns>
        public int MySqlInsertUser(UserInfoModel _userInfoModel)
        {
            conn.Open();
            string sqlstr = String.Format("insert into userinfo (name,pwd) values('{0}','{1}')",_userInfoModel.Name,_userInfoModel.Pwd);
            MySqlCommand cmd = new MySqlCommand(sqlstr, conn);
            int iRet = cmd.ExecuteNonQuery();
            conn.Close();
            return iRet;
        }

        /// <summary>
        /// 更新數據
        /// </summary>
        /// <param name="_userInfoModel"></param>
        /// <returns></returns>
        public int MySqlUpdateUserPwd(UserInfoModel _userInfoModel)
        {
            conn.Open();
            string sqlstr = String.Format("update userinfo set Pwd = '{0}' where name = '{1}'",_userInfoModel.Pwd,_userInfoModel.Name);
            MySqlCommand cmd = new MySqlCommand(sqlstr, conn);
            int iRet = cmd.ExecuteNonQuery();
            conn.Close();
            return iRet;
        }
    }
}

　　BLL是界面操作所做的相關處理，在BLL類庫中引用DAL和Model類庫，如下：

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using StudentDAL;
using StudentModel;

namespace StudentBLL
{
    public class UserInfoBLL
    {
        
        /// <summary>
        /// 判斷用戶是否存在
        /// </summary>
        /// <param name="name"></param>
        /// <param name="pwd"></param>
        /// <returns></returns>
        public bool CheckUserExist(string name,string pwd)
        {
            UserInfoModel user = new UserInfoModel();
            user.Name = name;
            user.Pwd  = pwd;
            UserInfoDAL userInfoDAL = new UserInfoDAL();
            UserInfoModel userInfoModel = userInfoDAL.MySqlSelectUser(user);

            if (userInfoModel.Name == name && userInfoModel.Pwd == pwd)
            {  
                return true;
            }
            else
            {
                return false;
            }
        }

        /// <summary>
        /// 判斷用戶名是否存在
        /// </summary>
        /// <param name="name"></param>
        /// <returns></returns>
        public bool CheckUserName(string name)
        {
            UserInfoModel user = new UserInfoModel();
            user.Name = name;
            UserInfoDAL userInfoDAL = new UserInfoDAL();
            UserInfoModel userInfoModel = userInfoDAL.MySqlSelectName(user);

            if (userInfoModel.Name == name)
            {
                return true;
            }
            else
            {
                return false;
            }
        }

        /// <summary>
        /// 查看所有的用戶
        /// </summary>
        public List<string> CheckAllUser()
        {
            List<UserInfoModel> userInfoModel = new List<UserInfoModel>();
            List<string> list = new List<string>();
            UserInfoDAL userInfoDAL = new UserInfoDAL();
            userInfoModel = userInfoDAL.MySqlSelectUserAll();

            for (int i = 0; i < userInfoModel.Count; i++)
            {
                list.Add(userInfoModel[i].Name);
            }

            return list;
        }

        /// <summary>
        /// 刪除所選中的用戶
        /// </summary>
        public bool DelSelUser(string selname)
        {
            UserInfoModel userinfomodel = new UserInfoModel();
            UserInfoDAL userinfodal = new UserInfoDAL();
            userinfomodel.Name = selname;
            if (userinfodal.MySqlDelUser(userinfomodel) > 0)
            {
                return true;
            }
            else
            {
                return false;
            }
        }

        /// <summary>
        /// 添加用戶
        /// </summary>
        /// <param name="name"></param>
        /// <param name="pwd"></param>
        public int InsertUser(string name, string pwd)
        {
            UserInfoModel userinfomodel = new UserInfoModel();
            UserInfoDAL userinfodal = new UserInfoDAL();

            userinfomodel.Name = name;
            userinfomodel.Pwd = pwd;

            if (CheckUserName(name) == true)
            {
                return -1;
            }
            else
            {
                return userinfodal.MySqlInsertUser(userinfomodel);
            }
        }

        /// <summary>
        /// 更新用戶密碼
        /// </summary>
        /// <param name="_userInfoModel"></param>
        /// <returns></returns>
        public bool UpdateUserPwd(string name,string pwd)
        {
            UserInfoModel userinfomodel = new UserInfoModel();
            UserInfoDAL userinfodal = new UserInfoDAL();

            userinfomodel.Name = name;
            userinfomodel.Pwd = pwd;

            if (userinfodal.MySqlUpdateUserPwd(userinfomodel) > 0)
            {
                return true;
            }
            else
            {
                return false;
            }

        }
    }
}

　　代碼已上傳至CSDN，鏈接如下：

https://download.csdn.net/download/qq_28091109/11292751

　　我是半路出家的外行，這也只是我個人學習記錄，大佬勿噴