Dynamic Control Loading

**wey97** · Mar 12th, 2010, 11:52 AM

I have a problem that I can't solve when I load controls dynamically. I have 3 states on a page that I traverse through and I load as many buttons on the page as the page state number + 1. For example, on state 0, I load 1 button, state 2 - 2 buttons, etc.

The problem is after I move to a new page state, the button click event(s) of the dynamic buttons will not be wired up and won't fire until the second click of each button.

CSharp Code:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
 
namespace WebTest
{
    public partial class DynamicButtonTest : System.Web.UI.Page
    {
        private int _PageState {
            get {
                if(ViewState["PageState"] != null) {
                    return (int)ViewState["PageState"];
                }
                return 0; // default
            }
            set {
                ViewState["PageState"] = value;
            }
        }
 
        private void LoadButtons(int pageState) {
 
            panelButtons.Controls.Clear();
 
            for(int i = 0; i < pageState + 1; i++) {
                Button b = new Button();
                b.Text = i.ToString();
                b.Click += new EventHandler(b_Click);
 
                panelButtons.Controls.Add(b);
            }
 
            _PageState = pageState;
        }
 
        void b_Click(object sender, EventArgs e) {
            Button b = (Button)sender;
            Response.Write("Button " + b.Text + " was clicked.");
        }
 
        protected void Page_Load(object sender, EventArgs e) {
 
            if(!IsPostBack) {
                LoadButtons(0);
            }
            else {
                LoadButtons(_PageState);
            }
        }
 
        protected void btnBack_Click(object sender, EventArgs e) {
 
            switch(_PageState) {
                case 0:
                    // Initial State - do nothing
                    break;
                case 1:
                    // move to PageState 0
                    LoadButtons(0);
                    break;
                case 2:
                    // move to PageState 1
                    LoadButtons(1);
                    break;
                default:
                    break;
            }
        }
 
        protected void btnNext_Click(object sender, EventArgs e) {
 
            switch(_PageState) {
                case 0:
                    // move to PageState 2
                    LoadButtons(1);
                    break;
                case 1:
                // move to PageState 3
                    LoadButtons(2);
                    break;
                case 2:
                    // Last State - do nothing
                    break;
                default:
                    break;
            }
        }
    }
}

PHP Code:


<&#37;@ Page Language="C#" AutoEventWireup="true" CodeBehind="DynamicButtonTest.aspx.cs" Inherits="WebTest.DynamicButtonTest" %>

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">

<html xmlns="http://www.w3.org/1999/xhtml" >
<head runat="server">
    <title></title>
</head>
<body>
    <form id="form1" runat="server">
    <div>
        <asp:Button ID="btnBack" runat="server" Text="Back" onclick="btnBack_Click" /><asp:Button ID="btnNext" runat="server" Text="Next" onclick="btnNext_Click" />
        <asp:Panel ID="panelButtons" runat="server">
        </asp:Panel>
    </div>
    </form>
</body>
</html>

**wey97** · Mar 12th, 2010, 12:07 PM

Page_Load could be simplifed to

CSharp Code:

protected void Page_Load(object sender, EventArgs e) {
    LoadButtons(_PageState);
}

**wey97** · Mar 12th, 2010, 01:44 PM

I found a way to make this work but it's far from ideal. Before I add a control to the panelButtons control collection, I check to see if a control with the same text already exists.

CSharp Code:

private void LoadButtons(int pageState) {
 
    for(int i = 0; i < pageState + 1; i++) {
        Button b = new Button();
        b.Text = i.ToString();
        b.Click += new EventHandler(b_Click);
 
        bool found = false;
 
        foreach(Control ctrl in panelButtons.Controls) {
 
            if(ctrl.GetType() == typeof(Button)) {
                Button btn = (Button)ctrl;
 
                if(btn.Text == b.Text) {
                    found = true;
                    break;
                } 
            }
        }
 
        if(!found) {
            panelButtons.Controls.Add(b);
        }
 
    }
 
    _PageState = pageState;
}

How can this be avoided?

EDIT:

Simplified way to not insert duplicate control.

CSharp Code:

private void LoadButtons(int pageState) {
 
    for(int i = 0; i < pageState + 1; i++) {
        Button b = new Button();
 
        b.ID = this.ID + "_button_" + i.ToString();
        b.Text = i.ToString();
        b.Click += new EventHandler(b_Click);
 
 
        if(panelButtons.FindControl(b.ID) == null) {
            panelButtons.Controls.Add(b);
        }
    }
    _PageState = pageState;
}

It still seems like there should be a more straightforward way to do this.

**gep13** · Mar 13th, 2010, 04:50 AM

Hey,

This is not a direct answer to your question by any means, but I would strongly recommend that you have a look at this article:

http://www.4guysfromrolla.com/articles/092904-1.aspx

Gary

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