Question

我正在为大学开设一个项目，我想说asp.net我很新。

请在下面找到我遇到问题的代码。问题是更新功能不起作用。在页面加载中，我有一些选择查询，我将数据库中的数据加载到一些textareas和textfields。这工作正常 - 它加载我在我的数据库中手动添加的示例数据。

我有按钮，应该在点击时更新数据库。

这是按钮的代码：

  <a id="A1"  class="button" onserverclick="box1_Click" runat="server">
        <span>Запази полето <img src="notification-tick.gif" width="12" height="12" /></span>
        </a>

这是背后的代码：

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


public partial class admin_Default : System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs e)
    {
        //Loading the data from the database

        string DatabaseConnectionString = System.Configuration.ConfigurationManager.ConnectionStrings["proekt"].ConnectionString;
        string sql1_title = "SELECT title FROM home WHERE id=1";
        string sql1_image = "SELECT image FROM home WHERE id=1";
        string sql1_text = "SELECT text FROM home WHERE id=1";

        string sql2_title = "SELECT title FROM home WHERE id=2";
        string sql2_image = "SELECT image FROM home WHERE id=2";
        string sql2_text = "SELECT text FROM home WHERE id=2";

        string sql3_title = "SELECT title FROM home WHERE id=3";
        string sql3_image = "SELECT image FROM home WHERE id=3";
        string sql3_text = "SELECT text FROM home WHERE id=3";
        using (SqlConnection conn = new SqlConnection(DatabaseConnectionString))
        {
            //box1 data load
            SqlCommand cmd1_title = new SqlCommand(sql1_title, conn);
            conn.Open();
            box1_title.Text = (string)cmd1_title.ExecuteScalar();
            conn.Close();
            SqlCommand cmd1_image = new SqlCommand(sql1_image, conn);
            conn.Open();
            box1_img.Text = (string)cmd1_image.ExecuteScalar();
            conn.Close();
            SqlCommand cmd1_text = new SqlCommand(sql1_text, conn);
            conn.Open();
            box1_text.InnerText = (string)cmd1_text.ExecuteScalar();
            conn.Close();

            //box2 data load
            SqlCommand cmd2_title = new SqlCommand(sql2_title, conn);
            conn.Open();
            box2_title.Text = (string)cmd2_title.ExecuteScalar();
            conn.Close();
            SqlCommand cmd2_image = new SqlCommand(sql2_image, conn);
            conn.Open();
            box2_img.Text = (string)cmd2_image.ExecuteScalar();
            conn.Close();
            SqlCommand cmd2_text = new SqlCommand(sql2_text, conn);
            conn.Open();
            box2_text.InnerText = (string)cmd2_text.ExecuteScalar();
            conn.Close();

            //box3 data load
            SqlCommand cmd3_title = new SqlCommand(sql3_title, conn);
            conn.Open();
            box3_title.Text = (string)cmd3_title.ExecuteScalar();
            conn.Close();
            SqlCommand cmd3_image = new SqlCommand(sql3_image, conn);
            conn.Open();
            box3_img.Text = (string)cmd3_image.ExecuteScalar();
            conn.Close();
            SqlCommand cmd3_text = new SqlCommand(sql3_text, conn);
            conn.Open();
            box3_text.InnerText = (string)cmd3_text.ExecuteScalar();
            conn.Close();
        }
    }

    protected void box1_Click(object sender, EventArgs e)
    {
        string DatabaseConnectionString = System.Configuration.ConfigurationManager.ConnectionStrings["proekt"].ConnectionString;
        string sql1 = "UPDATE home SET title=@title, image=@image, text=@text WHERE Id=1";
        using (SqlConnection conn = new SqlConnection(DatabaseConnectionString))
        {
            SqlCommand cmd2 = new SqlCommand(sql1, conn);

            cmd2.Parameters.AddWithValue("@title", box1_title.Text);
            cmd2.Parameters.AddWithValue("@image", box1_img.Text);
            cmd2.Parameters.AddWithValue("@text", box1_text.InnerText);

            conn.Open();
            cmd2.ExecuteNonQuery();
            conn.Close();
        }
    }

    protected void box2_Click(object sender, EventArgs e)
    {

    }


    protected void box3_Click(object sender, EventArgs e)
    {

    }
}

当我更改box1的标题然后单击按钮更新数据库时，它实际上刷新了页面并再次加载示例数据，我的更改未保存。

你可以帮我解决这个问题吗？没有任何错误。

非常感谢你们。

PS：我注意到当我在浏览器中加载页面然后删除数据加载的整个代码块时，在其中一个字段中对浏览器进行更改然后按下它实际更新的按钮数据库。这很奇怪......

Answer 1

这是因为您需要注意ASP.NET lifecycle。

您需要检查它是否PostBack（单击按钮时发生回发）或不... 或者你总是会覆盖你的数据。

 protected void Page_Load(object sender, EventArgs e)
 {
     if (!PostBack)
     {
          string DatabaseConnectionString = System.Configuration.ConfigurationManager.ConnectionStrings["proekt"].ConnectionString;
          string sql = "SELECT id,title,image,text FROM home WHERE id in (1,2,3) order by id";    
          using (SqlConnection conn = new SqlConnection(DatabaseConnectionString))
          {
          conn.Open();

搜索datareader - ＆gt;并在此处使用...将返回的数据保存到 datareader并按ID过滤，如果其项目/标题等如here和here

          conn.Close();
          }

     }    
 }

Answer 2

Fisrt，我想建议在Page_Load中，只打开一次sql连接，并在连接打开时执行所有命令，然后在结束时关闭它。这将使您的页面加载速度更快。

其次，您可以使用asp linkbutton在单击时创建回发。语法应如下所示：

<asp:LinkButton ID="A1" runat="server" OnClick="box1_Click">
    <span>Запази полето <img src="notification-tick.gif" width="12" height="12" /></span>
</asp:LinkButton>

ASP.NET C＃更新查询无法正常工作

2 个答案: