有人可以帮我修改此代码，使其在 C# ASP.NET 中工作吗？

Question

The user should be able to enter student id number in the textbox at the top of the form and all the information should be shown in the grid view order. The user should be able to click on the Return Book button to return the book

Note: I am not connecting to my database can someone correct this code please

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Data;
using System.Data.SqlClient;
using System.Configuration;
using System.Drawing;

namespace CHS_Online_Library.Admin 
{
  public partial class ReturnBooks: System.Web.UI.Page 
  {
    string str = ConfigurationManager.ConnectionStrings["connect"].ConnectionString;
    
    protected void Page_Load(object sender, EventArgs e) 
    {
      dataGridView1_bookreturn.DataSource = GetBookReturnList();
    }

    private DataTable GetBookReturnList() 
    {
      DataTable dtViewBook = new DataTable();

      using(SqlConnection con = new SqlConnection(str)) 
      {
        using(SqlCommand cmd = new SqlCommand("SELECT * FROM BookReturn", con)) 
        {
          con.Open();
          SqlDataReader reader = cmd.ExecuteReader();

          dtViewBook.Load(reader);
        }
      }

      return dtViewBook;
    }

    protected void BR_Return_Click(object sender, EventArgs e) 
    {
      SqlConnection con = new SqlConnection();
      con.ConnectionString = "";
      SqlCommand cmd = new SqlCommand();
      cmd.Connection = con;

      try 
      {
        con.Open();
        cmd.CommandText = "insert into BookReturn(StudentID, BookName,IssueDate,ReturnDate,) values('" + textBox_brsearch.Text + "', '" + BR_bookname.Text + "', '" + BR_issuedate.Text + "', '" + dateTimePicker1.Text + "')";
        cmd.ExecuteNonQuery();
        lblRMsg.Text = "Book was return successfully";
        lblRMsg.Visible = true;
        lblRMsg.ForeColor = Color.Green;

      } catch (Exception ex) {
        lblRMsg.Text = "Try Again";
        lblRMsg.Visible = true;
        lblRMsg.ForeColor = Color.Red;

      } finally {
        con.Close();
      }
    }

    protected void textBox_brsearch_TextChanged(object sender, EventArgs e) 
    {
      {
        SqlConnection con = new SqlConnection();
        con.ConnectionString = "";
        con.Open();
        if (textBox_brsearch.Text != "") 
        {
          SqlCommand cmd = new SqlCommand("Select BookName, IssueDate from IssueBook where StudentID =@StudentID", con);
          cmd.Parameters.AddWithValue("@StudentID", int.Parse(textBox_brsearch.Text));
          SqlDataReader da = cmd.ExecuteReader();
          while (da.Read()) {
            BR_bookname.Text = da.GetValue(0).ToString();
            BR_issuedate.Text = da.GetValue(1).ToString();

          }
          con.Close();
        }
      }

    }
  }
}

Answer 1

I don't know if I'm right, but looking at your code and with what you explain I think this is it.

protected void Page_Load(object sender, EventArgs e) 
{
    dataGridView1_bookreturn.DataSource = GetBookReturnList();
    dataGridView1_bookreturn.DataBind(); //you forget this part
}

See the reference .