时间：2021-07-01 10:21:17 帮助过：15人阅读
创建一个类，把整个数据库表单的数据都封装一下
数据访问类：
using System; using System.Collections.Generic; using System.Linq; using System.Text; using System.Data.SqlClient; namespace 实体类_和数据访问类.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.Nikename); cmd.Parameters.AddWithValue("@d", u.Sex); cmd.Parameters.AddWithValue("@e", u.Birthday); cmd.Parameters.AddWithValue("@f", u.Nation); cmd.Parameters.AddWithValue("@g", u._class1); try { conn.Open(); count = cmd.ExecuteNonQuery(); } catch { ok = false; } finally { conn.Close(); } if (count > 0) ok = true; return ok; } /// <summary> /// 通过泛型集合对数据进行查询 /// </summary> /// <returns>返回一个集合</returns> public List<Users> select() { List<Users> list = new List<Users>(); cmd.CommandText = "select ids,UserName,[PassWord],NickName,Sex,Birthday,NationName,ClassName from users join Nation on nation.NationCode=Users.Nation JOIN dbo on Users.Class=dbo.ClassCode "; conn.Open(); SqlDataReader dr = cmd.ExecuteReader(); if (dr.HasRows) { while (dr.Read()) { int p = 0; while(p<dr.FieldCount) { if(dr[p] is Boolean) { Console.Write((Boolean)dr[p]?"男":"女"+"\t"); } else if(dr[p] is DateTime) { Console.Write(" "+(((DateTime)dr[p]).ToShortDateString()) + "\t" + " "); } else Console.Write(dr[p]+"\t"); p++; } Console.WriteLine(); } } conn.Close(); return list; } /// <summary> /// 查询是否有此用户 /// </summary> /// <param name="usname"></param> /// <returns>有返回true</returns> public bool select(string usname) { bool has=false; cmd.CommandText = "SELECT *FROM Users where username=@a"; cmd.Parameters.Clear(); cmd.Parameters.AddWithValue("@a",usname); conn.Open(); SqlDataReader dr= cmd.ExecuteReader(); if (dr.HasRows) has = true; conn.Close(); return has; } /// <summary> /// 删除方法 /// </summary> /// <param name="usname"></param> public void delect(string usname) { cmd.CommandText = "DELETE FROM Users WHERE UserName=@a"; cmd.Parameters.Clear(); cmd.Parameters.AddWithValue("@a", usname); conn.Open(); cmd.ExecuteNonQuery(); conn.Close(); } public bool Update(string uname,string uname1,string uname2) { bool ok = false; int count = 0; cmd.CommandText = "update Users set "+uname1+"=@b where UserName = @a"; cmd.Parameters.Clear(); cmd.Parameters.AddWithValue("@a", uname); cmd.Parameters.AddWithValue("@b", uname2); try { conn.Open(); count = cmd.ExecuteNonQuery(); } catch { ok = false; } finally { conn.Close(); } if (count > 0) ok = true; return ok; } } }
注：
1、一般约定，在项目里新建一个叫做App_xx的文件夹，将实体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、数据访问类开头格式：
class userdata
{
SqlConnection conn = null;
SqlCommand cmd = null;
public userdata()
{
conn = new SqlConnection("server=.;database=Data0928;user=sa;pwd=123");
cmd = conn.CreateCommand();
}
4、匿名方法
例
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
有些方法也可以不用赋值直接进行调用
if (new userdata().select(uname))
namespace 泛型集合
{
class Program
{
static void Main(string[] args)
{
//创建泛型集合对象
List<int> list=new List<int>();
//添加原素1,2,3
list.Add(1);
list.Add(2);
list.Add(3);
//添加数组{1,2,3,4,5,6}
list.AddRange(new int[] {1,2,3,4,5,6});
//添加本身（泛型集合）
list.AddRange(list);
//清空 list.Clear();
//移除某个原素 list.Remove(1);
//移除一定范围的元素 list.RemoveRange(0,2);
//移除指定索引位置的原素 list.RemoveAt(3);
//原素反转 list.Reverse();
//原素升序排序 list.Sort();
//list泛型集合可以和数组互相转换
int[] nums = list.ToArray();
List<int> listint = nums.ToList();
//遍历集合
for (int i = 0; i < list.Count;i++ )
{
Console.WriteLine(list[i]);
}
Console.ReadKey();
}
}泛型集合
using System; using System.Collections.Generic; using System.Linq; using System.Text; using System.Data.SqlClient; using 实体类_和数据访问类.App_Code; namespace 实体类_和数据访问类 { class Program { static void Main(string[] args) { Console.Write("编号" + "\t" + "用户名" + "\t" + "密码" + "\t" + "昵称" + "\t" + "性别" + "\t" + "出生日期" + "\t" + "民族" + "\t" + "班级" + "\n"); //List<Users> ulist = new UsersData().select(); List<Users> wewe = new List<Users>(); UsersData udd=new UsersData(); wewe=udd.select(); foreach (Users uu in wewe) { Console.WriteLine(uu.Ids + "" + uu.Username + "" + uu.Password + "" + uu.Nikename + "" + uu.Sex + "" + uu.Birthday + "" + uu.NationName + "" + uu.ClassName); } for (; ; ) { Console.WriteLine("1.添加，2.删除，3.修改，4,查看"); Console.Write("请输入你要操作的序号："); string aa = Console.ReadLine(); if (aa == "1") { Users user = new Users(); Console.Write("请输入要添加的用户名"); user.Username = Console.ReadLine(); Console.Write("请输入要添加的密码"); user.Password = int.Parse(Console.ReadLine()); Console.Write("请输入要添加的昵称"); user.Nikename = Console.ReadLine(); Console.Write("请输入要添加的性别"); user.Sex = bool.Parse(Console.ReadLine()); Console.Write("请输入要添加的生日"); user.Birthday = DateTime.Parse(Console.ReadLine()); Console.Write("请输入要添加的民族"); user.Nation = Console.ReadLine(); Console.Write("请输入要添加的班级"); user._class1 = Console.ReadLine(); UsersData ud = new UsersData(); bool isok = ud.Insert(user); if (isok) { Console.WriteLine("添加成功"); } else Console.WriteLine("添加失败"); } else if(aa=="2") { Console.Write("请输入要删除的用户名："); string usname = Console.ReadLine(); if(new UsersData().select(usname)) { Console.WriteLine("已查到此用户,是否删除(Y,N)"); string cc = Console.ReadLine(); if(cc.ToUpper()=="Y") { new UsersData().delect(usname); Console.WriteLine("删除成功"); } else if(cc.ToUpper()=="N") { Console.WriteLine("取消了删除操作"); } else if(cc=="") { Console.WriteLine("请按提示操作"); } else Console.WriteLine("请按提示操作"); } else { Console.WriteLine("没有查到要删除的数据"); } } else if(aa=="3") { SqlConnection conn = new SqlConnection("server=;database=data0928;user=sa;pwd=123"); SqlCommand cmd = conn.CreateCommand(); Console.Write("请输入想要修改的用户名："); string z = Console.ReadLine(); cmd.CommandText = "select ids,UserName,[PassWord],NickName,Sex,Birthday,NationName,ClassName from users join Nation on nation.NationCode=Users.Nation JOIN dbo on Users.Class=dbo.ClassCode where username=‘" + z + "‘"; conn.Open(); SqlDataReader dw = cmd.ExecuteReader(); if (dw.HasRows) { while (dw.Read())//循环每一行 当超出时返回false { Console.WriteLine(dw["ids"] + "\t" + dw["UserName"] + "\t" + dw["PassWord"] + "\t" + dw["NickName"] + "\t" + (Convert.ToBoolean(dw["Sex"]) ? "男" : "女") + "\t" + Convert.ToDateTime(dw["Birthday"]).ToString("yyyy年MM月dd日") + "\t" + dw["NationName"] + "\t" + dw["ClassName"]); } conn.Close(); Console.Write("是否确定修改此条数据？(Y/N)"); string yn = Console.ReadLine(); if (yn.ToUpper() == "Y") { string uname = Console.ReadLine(); Console.Write("请输入密码："); string pwd = Console.ReadLine(); Console.Write("请输入昵称："); string nick = Console.ReadLine(); Console.Write("请输入性别："); string sex = Console.ReadLine(); Console.Write("请输入生日："); string bir = Console.ReadLine(); Console.Write("请输入民族："); string nation = Console.ReadLine(); Console.Write("请输入班级："); string cla = Console.ReadLine(); cmd.CommandText = "UPDATE Users set PassWord = ‘" + pwd + "‘,NickName = ‘" + nick + "‘,Sex=‘" + sex + "‘,Birthday=‘" + bir + "‘,Nation=‘" + nation + "‘,Class=‘" + cla + "‘ where UserName = ‘" + z + "‘"; conn.Open(); int ui = cmd.ExecuteNonQuery(); conn.Close(); if (ui > 0) { Console.WriteLine("修改成功"); } else { Console.WriteLine("修改失败"); } } else if (yn.ToUpper() == "N") { Console.WriteLine("取消了修改操作"); } else { Console.WriteLine("请按提示操作"); } } else { Console.WriteLine("没有此条数据"); } } else if(aa=="4") { Console.Write("编号" + "\t" + "用户名" + "\t" + "密码" + "\t" + "昵称" + "\t" + "性别" + "\t" + "出生日期" + "\t" + "民族" + "\t" + "班级" + "\n"); List<Users> asas = new List<Users>(); UsersData wdd = new UsersData(); asas = wdd.select(); foreach (Users uu in asas) { Console.WriteLine(uu.Ids + "\t" + uu.Username + "\t " + uu.Password + "\t" + uu.Nikename + "\t" + uu.Sex + "\t" + uu.Birthday + "\t" + uu.NationName + "\t" + uu.ClassName); } } else if (aa == "") { Console.WriteLine("请按提示操作"); } else { Console.WriteLine("请按提示操作"); } } } } }
防止SQL注入攻击，数据库操作类
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