1#数据库操作类  SqlHelper.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Data.SqlClient;
using System.Data;namespace stu
{class SqlHelper{private static string DbConfig = "Server=localhost;database=data_student;Trusted_Connection=True;";/// <summary>/// 对数据库进行 添加，修改，删除操作/// </summary>/// <param name="sql"></param>/// <returns></returns>public static int EditSql(string sql){SqlConnection conn = new SqlConnection();conn.ConnectionString = DbConfig;conn.Open();SqlCommand command = new SqlCommand(sql,conn);int count = 0;try{count = command.ExecuteNonQuery();}catch (Exception) {count = -1;Console.WriteLine("数据库写入失败!");}command.Dispose();conn.Close();return count;}/// <summary>/// 查询数据库，返回DataTable/// </summary>/// <param name="sql"></param>/// <returns></returns>public static DataTable LookUp(string sql){SqlConnection conn = new SqlConnection();conn.ConnectionString = DbConfig;conn.Open();SqlCommand command = new SqlCommand(sql, conn);SqlDataAdapter apter = new SqlDataAdapter();apter.SelectCommand = command;DataSet ds = new DataSet();apter.Fill(ds);DataTable table = ds.Tables[0];conn.Close();return table;}}
}

2# 实体类  UserModel.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;namespace stu
{public class UserModel{public string UserName { get; set; }public string PassWord { get; set; }public string NickName { get; set; }public string Gender { get; set; }public override string ToString(){return string.Format("UserName:{0}  PassWord:{1}  NickName:{2}  Gender:{3}",UserName,PassWord,NickName,Gender);}}}

3# 数据交换层 UserControl.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Data;
namespace stu
{public class UserControl{public static UserModel DataRowToUserModel(DataRow currentRow){UserModel user = new UserModel();user.UserName = currentRow["UserName"].ToString().Trim();user.PassWord = currentRow["PassWord"].ToString().Trim();user.NickName = currentRow["NickName"].ToString().Trim();user.Gender = currentRow["Gender"].ToString().Trim();return user;}/// <summary>/// 登录，如果返回null 说明不存在/// </summary>/// <param name="username"></param>/// <param name="pwd"></param>/// <returns></returns>public static UserModel Login(string username,string pwd){string sql = $"select * from TableUser where UserName='{username}' and PassWord='{pwd}'; ";DataTable table= SqlHelper.LookUp(sql);if (table.Rows.Count<=0) // 这里要用小于等于0{return null;}UserModel user = DataRowToUserModel(table.Rows[0]);return user;}/// <summary>/// 返回所有数据 /// </summary>/// <returns></returns>public static List<UserModel> ShowAllUsers(){List<UserModel> list = new List<stu.UserModel>();string sql = $"select * from TableUser";DataTable table= SqlHelper.LookUp(sql);if (table.Rows.Count<=0){return null;}for (int i = 0; i < table.Rows.Count; i++){UserModel model = DataRowToUserModel(table.Rows[i]);list.Add(model);}return list;}/// <summary>/// 修改用户信息/// </summary>/// <param name="user"></param>public static bool EditUserInfo(UserModel user){string sql = $"update TableUser SET password='{user.PassWord}',nickname='{user.NickName}',gender='{user.Gender}'where username='{user.UserName}'; ";int count = SqlHelper.EditSql(sql);if (count>=0){return true;}else{return false;}}}
}

界面层

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Data;namespace stu
{class Program{static void Main(string[] args){while (true){Console.WriteLine("欢迎进入登录系统....");Console.Write("输入用户名:");string name = Console.ReadLine();Console.Write("输入用户密码:");string pwd = Console.ReadLine();UserModel user = UserControl.Login(name, pwd);if (user==null){Console.WriteLine("不存在");continue;}else{Console.WriteLine("登录成功");break;}}List<UserModel> users = UserControl.ShowAllUsers();foreach (UserModel item in users){Console.WriteLine(item);}// 修改数据Console.WriteLine("------------------------------------------------------------------------"  );UserModel u = new UserModel() { UserName = "李阿猫", PassWord = "123456", NickName = "guoguo"};bool flag = UserControl.EditUserInfo(u);if (flag){Console.WriteLine("修改成功");}Console.ReadKey();}}
}