T-SQL 第十四章上机连接数据库

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Data.SqlClient;//SQL SEVER .NET 数据程序提供程序命名空间

namespace ConsoleApplication1
{
    class Program
    {
        private const string strconn = @"Data Source=.;Initial Catalog=MySchool;
                        Integrated Security=True";
        static void Main(string[] args)
        {
            
            Program p = new Program();
            p.delu();
           
            //string name = "admin"; //为声明项目可以不用特意声明他
            //string pwd = "0";     //为声明项目可以不用特意声明他
            //Console.WriteLine("请输入账号:");
            //string a = Console.ReadLine();
            //Console.WriteLine("请输入密码:");
            //string C = Console.ReadLine();
            //string Msg = " ";
       
            //bool b = p.chech(a, C, ref Msg);
            //if (b)
            //{
            //    p.show();
            //    Console.WriteLine(Msg);


            //}
            //else
            //{
            //    Console.WriteLine("你登陆失败!!!");
            //}
        
//////////////////////////////////////////////////////////////////////////////////////

        }
        public bool chech(string name,string pwd,ref string Msg) 
        {
            SqlConnection conn = new SqlConnection(strconn);//局部变量
            try
            {
               // SqlConnection conn = new SqlConnection(strconn);成员变量
                conn.Open();
                string str = @"SELECT COUNT(*) FROM [MySchool].[dbo].[Admin]
                        where LoginId='" + name + "'and LoginPwd='" + pwd + "'";
                Console.WriteLine(str);
                SqlCommand comm = new SqlCommand(str, conn);
                int o = (int)comm.ExecuteScalar(); //强制转换为 int 类型
                if (o > 0)
                {
                    Msg = "登陆成功";//引用传参 可以不写
                    return true;
                }
                Console.WriteLine(o);
            }
            catch (Exception ex)
            {

                Console.WriteLine("出现异常" + ex.Message);
             
            }
            finally 
            {
                conn.Close();  
            }
                
            return false;
        }
        public bool delu() ////登陆账户和密码
        {
            Console.WriteLine("请输入账号:");
            string a = Console.ReadLine();
            Console.WriteLine("请输入密码:");
            string C = Console.ReadLine();
            string Msg = " ";

            bool b = chech(a, C, ref Msg);
            if (b)
            {
               show();
                Console.WriteLine(Msg);
                return true;


            }
            else
            {
                Console.WriteLine("你登陆失败!!!");
                Console.WriteLine("请重新输入");
                return false;
            }


        }
        public void show() /////创建一个菜单//////////////////////
        {
            do
            {
                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. 删除学生记录");
                Console.WriteLine("0. 退出");
                Console.WriteLine("=========================");
                Console.WriteLine("请选择:");
                int num = int.Parse(Console.ReadLine());
                switch (num)
                {
                    case 1:
                        show1();
                        continue;
                    case 2:
                      
                        continue;
                    case 3:
                     
                        continue; ;
                    case 4:
                       
                        continue;
                    case 5:
                        
                        continue;
                    case 6:
                        
                        continue;
                    case 0:
                      
                        break;
                    default:
                        Console.WriteLine("输入错误");
                        continue;
                }
                break;
            } while (true);


        }
        public void show1() /////查询学生人数////////////////
        {
            SqlConnection conn = new SqlConnection(strconn);
            try
            {
                string str = "select count(*) from Student";
                conn.Open();
                SqlCommand comm = new SqlCommand(str, conn);
                int i = (int)comm.ExecuteScalar();
                Console.WriteLine("学生总人数为:" + i);

            }
            catch (Exception)
            {

                Console.WriteLine("出现异常");
            }
            finally 
            {
                conn.Close();
            }

        }
    }
}