asp.net, c#, 图片按钮事件处理程序

Question

我的代码中有以下两个图像按钮事件处理程序，对于动态添加的图像按钮，第一个在页面加载事件中调用并且事件处理程序正在触发（尽管我知道我需要将其移出页面加载事件），第二个在预渲染事件中调用，并且在单击按钮时不会触发事件处理程序。 这是代码，第一个（工作）：

protected void Page_Load(object sender, EventArgs e)
{
    // check if user logged in 
    if (Session["userID"] == null)
        Server.Transfer("login.aspx");

    else
    {
        try
        {
            // connect to db and get event info for user events
            using (SqlConnection connection = new SqlConnection(System.Configuration.ConfigurationManager.ConnectionStrings["UsersConnectionString1"].ConnectionString))
            {
                using (SqlCommand command = new SqlCommand())
                {
                    command.Connection = connection;
                    command.CommandType = System.Data.CommandType.StoredProcedure;
                    command.CommandText = "GetUserEvents";
                    command.Parameters.AddWithValue("@UserID", Session["UserID"]);
                    connection.Open();
                    using (SqlDataReader reader = command.ExecuteReader())
                    {
                        while (reader.Read())
                        {
                            //System.Diagnostics.Debug.Write(reader[1].ToString());

                            ImageButton anEvent = new ImageButton();
                            String eventid = reader[0].ToString();
                            anEvent.ImageUrl = "";
                            anEvent.Click += delegate(object sender2, ImageClickEventArgs e2) { anEvent_Click(sender, e, eventid); };

                            anEvent.ToolTip = (reader[1].ToString()) + "\n" + (reader[2].ToString()) + "\n" + (reader[3].ToString()) + "\n\n";

                            Panel3.Controls.Add(anEvent);
                            Panel3.Controls.Add(new LiteralControl("&nbsp &nbsp"));
                        }
                    }
                }
            }
        }

        catch (Exception ex)
        {
            //error handling...
        }
    }
}

protected void anEvent_Click(object sender, EventArgs e, string eventid)
{   
    // create session variable to identify event info for event page for specific event user clicks on
    Session["eventID"] = eventid;     
    Server.Transfer("Event.aspx");    
}

第二个（不工作）：

protected override void OnPreRender(EventArgs e)
{
    UpdateNewsFeed();
    LoadUserEvents();
}


private void LoadUserEvents()
{
    try
    {
        // connect to db and get event info for user events
        using (SqlConnection connection = new SqlConnection(System.Configuration.ConfigurationManager.ConnectionStrings["UsersConnectionString1"].ConnectionString))
        {
            using (SqlCommand command = new SqlCommand())
            {
                command.Connection = connection;
                command.CommandType = System.Data.CommandType.StoredProcedure;
                command.CommandText = "GetUserEvents";
                command.Parameters.AddWithValue("@UserID", Session["UserID"]);
                connection.Open();
                using (SqlDataReader reader = command.ExecuteReader())
                {
                    while (reader.Read())
                    {
                        //System.Diagnostics.Debug.Write(reader[1].ToString());

                        ImageButton anEvent = new ImageButton();
                        String eventid = reader[0].ToString();
                        anEvent.Click += delegate(object sender2, ImageClickEventArgs e2) { anEvent_Click(sender2, e2, eventid); };
                        anEvent.ImageUrl = reader[4].ToString();
                        anEvent.ToolTip = (reader[1].ToString()) + "\n" + (reader[2].ToString()) + "\n" + (reader[3].ToString()) + "\n\n";

                        EventsPanel.Controls.Add(anEvent);
                        EventsPanel.Controls.Add(new LiteralControl("&nbsp &nbsp"));
                    }
                }
            }
        }
    }

    catch (Exception ex)
    {
        //error handling...
    }
}

protected void anEvent_Click(object sender, EventArgs e, String eventid)
{
    Session["eventID"] = eventid;
    Server.Transfer("Event.aspx");
}

我假设这与对象有关，并且发送者未正确传递，但如果没有在页面加载事件中调用的方法，我不知道该怎么做这样做意味着按钮在回发时消失。

任何建议将不胜感激，谢谢大家！

Answer 1

您在第二个示例中的page life cycle 中添加控件（OnPreRender）为时已晚。 .尝试 PreInit 作为 MSDN 推荐或 Init 或 Load 在更糟糕的情况下您需要访问会话。