ASP.NET Detailed explanation of the steps to realize the library management system

try
 {
  //Give SQL string data
  string strsql1 = "insert into yhxx (zh,mima) values ('" + Tet_zh.Text + "','" + Tet_mima.Text + "')";
  //Create string object
  mycom = new SqlCommand(strsql1, myconn);
  mycom.ExecuteNonQuery();
  //Close the database
  myconn.Close();
  Response.Write ("< script > alert ('added successfully!)!! ')</script>");
  //Save account number
  //str = Tet_zh.Text;
  //Save user name
  Application["name"] = Tet_zh.Text;
  //If successful, successful transfer in
  Response.Redirect("Useradd.aspx");
 }
 catch (Exception ex)
 {
  Response.Write ("< script > alert ('user already exists!! ')</script>");
 }

protected void tianjia()
 {
 //Add user information
 try
 {
  //Give SQL string data
  
  string strsql1 = "update yhxx set xm='"+Tet_xm.Text+"',xb='"+tet_xb.Text+"',qq='"+Tet_qq.Text+"',Email='"+Tet_email.Text+"',dizhi='"+tet_home.Text+"',enjioy='"+Tet_enjoy.Text+"' where zh='"+Application["name"]+"'";
  //Create string object
  mycom = new SqlCommand(strsql1, myconn);
  mycom.ExecuteNonQuery();
  //Close the database
  myconn.Close();
  Response.Write ("< script > alert ('added successfully!)!! ')</script>");
  Response.Redirect("denglu.aspx");
 }
 catch (Exception ex)
 {
  Response.Write ("< script > alert ('add failed!! ')</script>"+ ex.Message.ToString ());
 }
 }

//Ordinary user login, administrator login is the same
 try
 {
  string sql = "select * from yhxx where zh='"+Tet_zh.Text+"' and mima='"+Tet_mm.Text+"' and yhlb='"+tet_dz.Text+"'";
  //Create command object
  SqlCommand com = new SqlCommand(sql,myconn);
  //Create read object
  SqlDataReader dr = com.ExecuteReader();
  //The prompt box pops up successfully
  // MessageBox.Show (read successfully!)!! ");
  if (dr.Read())
  {
  dr.Close();
  myconn.Close();
  Application["name1"] = Tet_zh.Text;
  Response.Redirect("index.aspx");
  }
  else
  {
  Response.Write ("< script > alert ('wrong user name or password!! ')</script>");
  }

 }
 catch (Exception ex)
 {
  Response.Write ("< script > alert ('login failed!! ')</script>");
 }

try
 {
  //Open database
  myconn.Open();
 }
 catch (Exception ex)
 {
  Response.Write ("< script > alert ('Database open failed ') < / script >");
 }
 try
 {
  //Create data string
  if (tet_name.Text == "")
  {
  Response.Write ("< script > alert ('name cannot be empty! ')</script>");
  }
  else
  {
  String strsql3 = "select bookid as book number, bookname as book name,"
    +"Booklb as book category, bookzz as book author, booklr as book content,"
    +"Bookfm as book cover, bookjg as book price, bookzt as book borrowing status"
    + " from Bookxx where BookName='" + tet_name.Text + "'";
  mycom = new SqlCommand(strsql3, myconn);
  //Open database
  //myconn.Open();
  //
  myread = mycom.ExecuteReader();
  GridView1.DataSource = myread;
  GridView1.DataBind();
  GridView1.Visible = true;
  //Close data
  myread.Close();
  myconn.Close();
  }
 }
 catch (Exception ex)
 {
  Response.Write ("< script > alert ('query failed! ')</script>" +  ex.Message.ToString ());
 }

1. Add books first
 if (myread.Read())
 {
  if (tet_zt.Text == "0")
  {
  //Add borrowing information table
  myread.Close();
  string strsql5 = "insert into Bookjyxx (ISBookID,ISBookname,ISBookzt,ISname,ISid) " +
  " values (" + Tet_Bookid.Text + ",'" + tet_Name.Text + "'," + tet_zt.Text + ",'" + Tet_xm.Text + "'," + Tet_ID.Text + ")";
  mycom = new SqlCommand(strsql5, myconn);
  mycom.ExecuteNonQuery();
  //Closing
  myconn.Close();
  myread.Close();
 //////////////////////////////////////
  xiugai();
  chaxun();
  }
  if (tet_zt.Text == "1")
  {
  Response.Write ("< script > alert ('the book is being borrowed ') < / script >");
  chaxun();
  }
 2. Modify the borrowing status
  //Create
 //First modify the status information of the book table
 string strsql7 = "update Bookxx set Bookzt='1' where BookID='" + Tet_Bookid.Text + "'";
 mycom = new SqlCommand(strsql7, myconn);
 myconn.Close();
 myconn.Open();
 mycom.ExecuteNonQuery();
 //Then modify the borrowing status table information
 string strsql8 = "update Bookjyxx set ISBookzt='1' where ISBookID='" + Tet_Bookid.Text + "'";
 mycom = new SqlCommand(strsql8, myconn);
 mycom.ExecuteNonQuery();
 Response.Write ("< script > alert ('borrowing succeeded! ')</script>");
 //Closing
 myconn.Close();

//Delete his borrowing information
 string strsql3="delete from bookjyxx where ISid='"+Tet_id.Text+"'";
 mycom = new SqlCommand(strsql3, myconn);
 myconn.Open();
 mycom.ExecuteNonQuery();
 //////////////////////////////
 //Refresh information
 //Query information
 String strsql4 = "select isname as borrower, ISID as card number, isbookid as book number,"
  +"Isbookname as borrowing data name, isbookzt as borrowing status, IsDate as borrowing date from bookjyxx where ISID = '" + Tet_ id.Text  + "'";
 mydata = new SqlDataAdapter(strsql4, myconn);
 DataSet set = new DataSet();
 mydata.Fill(set);
 GridView1.DataSource = set.Tables[0];
 GridView1.DataBind();
 GridView1.Visible = true;
 //Modification status
 //First modify the status information of the book table
 string strsql7 = "update Bookxx set Bookzt='0' where BookID='" +tet_Bookid.Text+ "'";
 mycom = new SqlCommand(strsql7, myconn);
 mycom.ExecuteNonQuery();
 Response.Write ("< script > alert ('returned successfully ') < / script >");
 //Closing
 myconn.Close();
 set.Clear();