ASP.NET (C#) 中的动态按钮问题

Question

我有一个搜索功能，可以在我的 OleDb 数据库中查找特定用户。对于每个用户，都会在表中创建一行，其中包含他的姓名、布尔值表示他是否是管理员以及一个删除按钮。删除按钮没有按预期工作，它不执行链接到它的方法。我的代码位于 Search_Click 事件中，该事件在管理员单击搜索按钮以搜索特定用户后立即执行。 我试图从我的代码中放置一个预定义的按钮，但在 Page_Load 中，它按预期工作。我怎样才能让按钮也从 Search_Click 工作？ 基本上，在根据用户搜索文本动态创建 LinkBut​​tons 并单击搜索按钮 (Search_Click) 之后，我需要找到一种方法来在页面加载事件上注册 click 事件，我不知道该怎么做，因为 linkbuttons 必须在搜索按钮的点击事件中创建，但它们也必须通过页面加载进行注册。

using (OleDbDataReader reader = cmd.ExecuteReader())
{
    Table table = new Table();
    TableRow row = new TableRow();
    TableCell cell = new TableCell();
    Label label = new Label();
    while (reader.Read())
    {
        row = new TableRow();
        cell = new TableCell();
        label = new Label();

        label.Text = reader.GetString(0);
        cell.Controls.Add(label);
        cell.BorderStyle = BorderStyle.Solid;
        row.Cells.Add(cell);

        cell = new TableCell();
        label = new Label();

        label.Text = reader.GetBoolean(1).ToString();
        cell.Controls.Add(label);
        cell.BorderStyle = BorderStyle.Solid;
        row.Cells.Add(cell);

        cell = new TableCell();
        LinkButton button = new LinkButton();

        button.Text = "Delete";
        button.ID = (string) reader["uName"];
        button.CommandName = (string)reader["uName"];
        button.Click += new EventHandler(DeleteUser);

        cell.Controls.Add(button);
        cell.BorderStyle = BorderStyle.Solid;
        row.Cells.Add(cell);

        table.Rows.Add(row);
    }
    table.Style.Add(HtmlTextWriterStyle.MarginLeft, "auto");
    table.Style.Add(HtmlTextWriterStyle.MarginRight, "auto");
    TableHolder.Controls.Add(table);
}

删除用户：

 protected void DeleteUser(object sender, EventArgs e)
    {
        try
        {
            LinkButton button = (LinkButton)sender;
            string path = Server.MapPath(@"App_Data/ArcadeDatabase.accdb");
            using (OleDbConnection con = new OleDbConnection("Provider=Microsoft.ACE.OLEDB.12.0;Data Source=" + path + "; Persist Security Info = False;"))
            {
                try
                {
                    con.Open();
                }
                catch(Exception ex)
                {
                    helper.Log("OleDbError", ex.Message);
                }
                if(con.State == System.Data.ConnectionState.Open)
                {
                    using (OleDbCommand cmd = new OleDbCommand("DELETE * FROM ArcadeDatabase WHERE uName ='" + button.CommandName + "';", con))
                    {
                        try
                        {
                            cmd.ExecuteNonQuery();
                        }
                        catch (Exception ex)
                        {
                            helper.Log("OleDbError", ex.Message);
                        }
                    }
                }
                con.Dispose();
            }
            path = "";
        }
        catch (Exception ex)
        {
            helper.Log("Admin", ex.Message);
        }
    }

Answer 1

动态控件的事件处理程序需要在Page_Load/Page_Init事件期间注册才能触发(see this link)。

因此，您必须在 page_load 或 init 中添加删除按钮及其事件处理程序。在 Page_Init 事件中查找导致回发的控件的 ID，see this

---

更新：

好的，我添加此代码以证明它可以毫无问题地完成。

要查看它是如何工作的：创建一个新的Web Form 并将以下 HTML 和 Code-Behinds 粘贴到其中。然后运行应用程序并在Search TextBox 中输入一些名称（例如：John 或Ali），然后按Search Button 过滤结果。

public partial class _Default : Page
{
    protected void Page_Load(object sender, EventArgs e)
    {
        string searchName = "";
        if (SearchTextBox.Text != "") //if (this.GetPostBackControlUniqueID() == Search.UniqueID) //Search button is clicked! 
        {
            searchName = SearchTextBox.Text;
        }
        addTable(searchName);
    }

    void addTable(string searchName)
    {
        string[] data = new[] { 
             "John, false, usrJohn"
            ,"Alex, false, usrAlex"
            ,"Ali,  true,  usrAli" 
        };

        //using (OleDbDataReader reader = cmd.ExecuteReader())
        //{
            Table table = new Table(); table.CellPadding = 10;
            TableRow row;
            TableCell cell;
            Label label;

            foreach(string dataItem in data) //while (reader.Read())
            {
                string[] reader = dataItem.Split(',');
                if (reader[0].IndexOf(searchName, StringComparison.OrdinalIgnoreCase) < 0) continue; //search not found (in real app, you use sql where clause for this, but this is just for test)

                row = new TableRow();
                cell = new TableCell();
                label = new Label();

                label.Text = reader[0].Trim(); //reader.GetString(0);
                cell.Controls.Add(label);
                cell.BorderStyle = BorderStyle.Solid;
                row.Cells.Add(cell);

                cell = new TableCell();
                label = new Label();

                label.Text = reader[1].Trim(); //reader.GetBoolean(1).ToString();
                cell.Controls.Add(label);
                cell.BorderStyle = BorderStyle.Solid;
                row.Cells.Add(cell);

                cell = new TableCell();
                LinkButton button = new LinkButton();

                button.Text = "Delete";
                string uName = reader[2].Trim();
                button.ID = uName; //(string)reader["uName"];
                button.CommandName = uName; //(string)reader["uName"];
                button.Click += new EventHandler(DeleteUser);

                cell.Controls.Add(button);
                cell.BorderStyle = BorderStyle.Solid;
                row.Cells.Add(cell);

                table.Rows.Add(row);
            }

            table.Style.Add(HtmlTextWriterStyle.MarginLeft, "auto");
            table.Style.Add(HtmlTextWriterStyle.MarginRight, "auto");

            TableHolder.Controls.Add(table);
        //} //end using OleDbDataReader reader
    }

    protected void Search_Click(object sender, EventArgs e)
    {
        //addTable(SearchTextBox.Text); //already done in Page_Load
    }

    protected void DeleteUser(object sender, EventArgs e)
    {

        LinkButton button = (LinkButton)sender;
        //using (OleDbCommand cmd = new OleDbCommand("DELETE * FROM ArcadeDatabase WHERE uName ='" + button.CommandName + "';", con))
        string sql = "DELETE * FROM ArcadeDatabase WHERE uName ='" + button.CommandName + "';";
        //execute the sql ... (in real app)

        TableHolder.Controls.Add(new LiteralControl("The sql was: " + sql));
    }

    protected void Button1_Click(object sender, EventArgs e)
    {
        Label1.Text = DateTime.Now.ToString("HH:mm:ss");
    }


} //end class

这是获取UniqueID 的PostBack 控件的辅助扩展方法：

// ***********************************************************************
public static class MyWebPageExtensions
{

    public static string GetPostBackControlUniqueID(this Page page)
    {
        if (!page.IsPostBack)
            return string.Empty;

        Control control = null;

        string controlName = page.Request.Params["__EVENTTARGET"]; //this method works only for link buttons which use javascript: __doPostBack(...) and not input type=submit buttons. Note: it is also available in Request.Form collection but this doesn't require to loop over Form.
        if (!String.IsNullOrEmpty(controlName))
        {
            control = page.FindControl(controlName);
        }
        else
        {
            // __EVENTTARGET is null, the control is a button (not javascript linkButton), we need to iterate over the form collection to find it
            foreach (string id in page.Request.Form)
            {
                // handle ImageButton they having an additional "quasi-property" in their Id which identifies mouse x and y coordinates
                if (id.EndsWith(".x") || id.EndsWith(".y"))
                {
                    string id2 = id.Substring(0, id.Length - 2);
                    control = page.FindControl(id2);
                }
                else
                {
                    control = page.FindControl(id);
                }

                if (control is IButtonControl) break;

            }
        }

        return control == null ? String.Empty : control.UniqueID;
    }

}