第十四章

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

namespace MySchoolBase
{
    class DBOperation
    {
        //连接字符串
        private const string conn = "Data Source=.;Initial Catalog=MySchool;Integrated Security=True";
        SqlConnection con = new SqlConnection(conn);
        static void Main(string[] args)
        {
           DBOperation dno=new DBOperation();
           dno.login();
           
          
            Console.ReadLine();
        }
        public void login()
        {
            Console.WriteLine("请输入用户名");
            string name = Console.ReadLine();
            Console.WriteLine("请输入密码");
            string mima = Console.ReadLine();
            bool r=Check(name, mima);
            if (r)
            {

                Console.WriteLine("登录成功");
                Console.WriteLine("********请选择操作键************");
                Console.WriteLine("1: 统计学生人数");
                Console.WriteLine("2: 查看学生名单");
                Console.WriteLine("3: 按学号查询学生姓名");
                Console.WriteLine("4: 按姓名查询学生信息");
                Console.WriteLine("5: 修改学生出生日期");
                Console.WriteLine("6: 修改学生记录");
                Console.WriteLine("7: 新增年级记录");
                Console.WriteLine("0: 退出");
                int n=int.Parse(Console.ReadLine());
                switch(n)
                {
                    case 1:
                        Amout();
                        break;
                    case 2:
                    case 3:
                    case 0:
                        break;

                }


            }
            else {

                Console.WriteLine("登录失败");
            
            
            }
        }
        public bool Check(string name,string mima)
        { 
            //创建数据库
             SqlConnection con = new SqlConnection(conn);
              try
            { 
                  string stra="SELECT COUNT(*) FROM Admin where LoginId='"+name+"' and LoginPwd='"+mima+"'";
                con.Open();
                  SqlCommand comm=new SqlCommand(stra,con);
                  int i=(int)comm.ExecuteScalar();
                    
               
            }
            catch (Exception ex)
            {

                Console.WriteLine("出现异常"+ex.Message);
            }
            finally
            { 
             con.Close();
                Console.WriteLine("关闭数据库");
            }
        return true;
        }
        public int Amout()
        {

            try
            {
                string stra = "SELECT COUNT(*) FROM Student";
                con.Open();
                SqlCommand comm = new SqlCommand(stra, con);
                int i = (int)comm.ExecuteScalar();
                Console.WriteLine("在校学生人数"+i);
                return i;
            }
            catch (Exception)
            {

                return -1;
            }
            con.Close();
        }
    }
}