每周总结【2020/12/20】——大作业准备

　　本周周一和周四分别进行了编译原理和设计模式的考试，随着考试结束这两门课程的知识暂且放下了。第17周有几门课程需要验收大作业，因此需要做一做。

　　周末这段时间我重学了一遍.NET编程，并使用C#自己编写了一个简易的图书管理系统，总代码行数500左右，因为使用C#编程时界面直接调用控件排列即可，所以需要编写的地方只需要后台连接数据库和页面传参等等。下面给出一些代码片段和截图。

　　查询与删除：

private void button1_Click(object sender, EventArgs e)
        {
            if (textBox1.Text == "")
            {
                MessageBox.Show("查询条件不能为空！");
            }
            else
            {
                string connsqlserver = "Data Source=LAPTOP-983LEFQ7;Initial Catalog=BOOK;User ID=sa;Pwd=Yuyuko";
                string sql = "";
                if (kind == "all")
                {
                    sql = "select * from books where bookname like '%{0}%'";
                }
                else
                {
                    sql = "select * from books where bookname like '%{0}%' and bookkind='" + kind + "'";
                }
                SqlConnection conn = new SqlConnection(connsqlserver);
                conn.Open();
                try
                {
                    sql = string.Format(sql, textBox1.Text);
                    SqlDataAdapter sda = new SqlDataAdapter(sql, conn);
                    DataSet ds = new DataSet();
                    sda.Fill(ds);
                    dataGridView1.DataSource = ds.Tables[0];
                }
                catch (Exception msg)
                {
                    MessageBox.Show("查询错误！" + msg.Message);
                }
                finally
                {
                    conn.Close();
                }
            }
        }

        private void button2_Click(object sender, EventArgs e)
        {
            string bookid = dataGridView1.SelectedRows[0].Cells[0].Value.ToString();
            string bookfrom = dataGridView1.SelectedRows[0].Cells[4].Value.ToString();
            if (bookfrom != username)
            {
                MessageBox.Show("不可删除其他用户上传的书！");
            }
            else
            {
                if (MessageBox.Show("确认删除么？", "确认", MessageBoxButtons.YesNo) == DialogResult.Yes)
                {
                    string connsqlserver = "Data Source=LAPTOP-983LEFQ7;Initial Catalog=BOOK;User ID=sa;Pwd=Yuyuko";
                    string sql = "delete from books where bookid='" + bookid + "'";
                    SqlConnection conn = new SqlConnection(connsqlserver);
                    conn.Open();
                    try
                    {
                        SqlCommand cmd = new SqlCommand(sql, conn);
                        int res = cmd.ExecuteNonQuery();
                        if (res > 0)
                        {
                            MessageBox.Show("删除成功！");
                            this.kind = "all";
                            QueryAllBook();
                        }
                        else
                        {
                            MessageBox.Show("删除失败！");
                        }
                    }
                    catch (Exception msg)
                    {
                        MessageBox.Show("删除错误！" + msg.Message);
                    }
                    finally
                    {
                        conn.Close();
                    }
                }
            }
        }

　　遍历：

 private void QueryAllBook()
        {
            string connsqlserver = "Data Source=LAPTOP-983LEFQ7;Initial Catalog=BOOK;User ID=sa;Pwd=Yuyuko";
            string sql = "";
            if (kind == "all")
            {
                sql = "select * from books";
            }
            else
            {
                sql = "select * from books where bookkind='" + kind + "'";
            }
            SqlConnection conn = new SqlConnection(connsqlserver);
            conn.Open();
            try
            {
                SqlDataAdapter sda = new SqlDataAdapter(sql, conn);
                DataSet ds = new DataSet();
                sda.Fill(ds);
                dataGridView1.DataSource = ds.Tables[0];
                dataGridView1.Columns[0].HeaderText = "书籍编号";
                dataGridView1.Columns[1].HeaderText = "书籍名称";
                dataGridView1.Columns[2].HeaderText = "书籍种类";
                dataGridView1.Columns[3].HeaderText = "书籍简介";
                dataGridView1.Columns[4].HeaderText = "上传用户";
                dataGridView1.ReadOnly = true;
                dataGridView1.AllowUserToAddRows = false;
                dataGridView1.MultiSelect = false;
                dataGridView1.SelectionMode = DataGridViewSelectionMode.FullRowSelect;
            }
            catch(Exception msg)
            {
                MessageBox.Show("遍历错误！" + msg.Message);
            }
            finally
            {
                conn.Close();
            }
        }

　　添加与修改的代码与上述类似，本质上都是使用SQL语句，这次进行数据操作所使用的数据库为SQLServer数据库，平时写JavaWeb的时候用的是MySQL。

 　　界面做得很简陋，不过基本的增删改查都有。