?using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Text;
using System.Windows.Forms;
using System.Data.SqlClient;

namespace 圖書館管理系統
{
    public partial class Form3 : Form
    {
        public Form3()
        {
            InitializeComponent();
        }

        private void button1_Click(object sender, EventArgs e)
        {
            if (this.textBox1.Text == "")
            {
                MessageBox.Show("請輸入圖書編號！");
            }
            else
            {
                SqlConnection myConnection = new SqlConnection();
                string conStr = "server=localhost;integrated security=sspi;database=pubs";
                myConnection.ConnectionString = conStr;
                myConnection.Open();
                //確認給圖書編號存在
                SqlCommand sc3 = new SqlCommand("select num from books where bid="+this .textBox1 .Text ,myConnection );
                SqlDataReader sdr3 = sc3.ExecuteReader();
                if (sdr3.Read())
                {
                    int num = Convert.ToInt32(sdr3.GetValue(0));
                    sdr3.Close();
                    //確認該書確實外借過
                    SqlCommand sc4 = new SqlCommand("select borrowDate from states where returnDate='0'and bid='" + this.textBox1.Text + "'", myConnection);
                    SqlDataReader sdr4 = sc4.ExecuteReader();
                    if (sdr4.Read())
                    {
                        System.DateTime bDate = Convert.ToDateTime(sdr4.GetValue(0));
                        // 計算借書時間
                        int d = System.DateTime.Now.DayOfYear - bDate.DayOfYear;
                        sdr4.Close();
                        //更改還書時間
                        String date = Convert.ToString(System.DateTime.Now);
                        SqlCommand sc1 = new SqlCommand("update states set returnDate='" + date + "'where bid='" + this.textBox1.Text + "'and returnDate='" + 0 + "'", myConnection);
                        sc1.ExecuteNonQuery();
                        //更改庫存圖書數目
                        SqlCommand sc2 = new SqlCommand("update books set num=" + Convert.ToString(num + 1) + "where bid ='" + this.textBox1.Text + "'", myConnection);
                        sc2.ExecuteNonQuery();
                        //檢驗借書時間是否超過30天
                        if (d > 30)
                        {
                            MessageBox.Show("借書超期" + Convert.ToString(d - 30) + " 天，罰款！");
                        }
                        MessageBox.Show("歸還成功 ");
                    }
                    else
                    {
                        sdr4.Close();
                        MessageBox.Show(" 該書從未外借過！");
                    }
                }
                else
                {
                    sdr3.Close();
                    MessageBox.Show("該書編號非法！");
                }
                myConnection.Close();
            }
        }

        private void button2_Click(object sender, EventArgs e)
        {
            this.Close();
        }
    }
}