14章 上机3-5

using System;
using System.Collections.Generic;
using System.Data.SqlClient;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
namespace ConsoleApplication3
{
    class DBOperation
    {
        private const string strConn = @"Data Source=.;Initial Catalog=MySchool;User ID=bdqn;Password=11";
        public bool CheckUserInfo(string userName,string pwd) {
            SqlConnection conn = new SqlConnection(strConn);
          try
          {
                string sql = @"SELECT count(*)FROM [MySchool].[dbo].[Admin] where LoginId='" + userName + "' and Loginpwd='" + pwd + "'";
                conn.Open();
                SqlCommand c = new SqlCommand(sql,conn);
                int i = (int)c.ExecuteScalar();
                if (i > 0)
                {
                    return true;
                }
              }
            catch (Exception ex)
            {
                Console.WriteLine(ex.Message);
            }
            conn.Close();
            return false;
        }
        public void cz() {
              do{
            Console.WriteLine("============选择操作键================");
            Console.WriteLine("1.统计学生人数");
            Console.WriteLine("2.查看学生名单");
            Console.WriteLine("3.按学号查询学生的姓名");
            Console.WriteLine("4.按姓名查询学生的信息");
            Console.WriteLine("5.修改学生出生日期");
            Console.WriteLine("6.删除学生记录");
            Console.WriteLine("7.新增年级记录");
            Console.WriteLine("0.退出");
            Console.WriteLine("======================================");
            int i=(int.Parse)(Console.ReadLine());
                  if(i==0){
                      break;
                  }
            switch(i){
                case 1: Console.WriteLine("查询学生人数:");
                  int s=GA();
                    if(s==-1){
                        Console.WriteLine("输入错误!");
                    }else{
                        Console.WriteLine(s);
                    }
                    break;
                case 2:
                    break;
                case 3:
                    break;
                case 4:
                    break;
                case 5:
                    break;
                case 6:
                    break;
                case 7:
                    break;
                case 0: Console.WriteLine("已退出!!");
                    break;
                default:
                    continue;
            }  
              }while(true);
            
          
        }
        public int GA() {
            SqlConnection conn = new SqlConnection(strConn);
            string strSql = "SELECT COUNT(*)FROM [MySchool].[dbo].[Student]";
            try
            {
                conn.Open();
                SqlCommand comm = new SqlCommand(strSql, conn);
                int i = (int)comm.ExecuteScalar();
                return i;
            }
            catch (Exception)
            {
                return -1;
            }
            finally {
                conn.Close();
            }
        }
    }
}

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

namespace ConsoleApplication3
{
    class Program
    {

        static void Main(string[] args)
        {
            DBOperation s = new DBOperation();
            Console.WriteLine("请输入账号:");
            string a = Console.ReadLine();
            Console.WriteLine("请输入密码:");
            string c = Console.ReadLine();
           
            bool i = s.CheckUserInfo(a, c);
            if (i)
            {
                Console.WriteLine("登陆成功");
            }
            else
            {
                Console.WriteLine("登陆失败");
            }
            s.cz();
            s.GA();
            Console.ReadLine();

          
        }
    }
}