Dynamically removing controls

Hi all,

My problem is pretty simple: I want to be able to click + and - buttons to add or remove text boxes. Adding works fine but when removing you have to click on the button twice. I've searched around and seen the same issue elsewhere but somehow I'm not quite able to grasp what changes I need to make to my own code. Any help would be greatly appreciated.

Here's the aspx file contents:

<%@ Page language="c#" Codebehind="AddingDropdowns.aspx.cs" AutoEventWireup="false" Inherits="ARD.Dev.Assets.AddingDropdowns"%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN" >
    <form id="Form1" method="post" runat="server">
      <asp:Button id="AddDropdown" runat="server" Text="+"></asp:Button><asp:Button id="RemoveDropdown" runat="server" Text="-"></asp:Button>
      <div id="DropdownPanel" runat="server"></div>

and here's the code:

namespace ARD.Dev.Assets
 /// <summary>
 /// Summary description for AddingDropdowns.
 /// </summary>
 public class AddingDropdowns : System.Web.UI.Page
  protected System.Web.UI.WebControls.Button AddDropdown;
  protected System.Web.UI.WebControls.Button RemoveDropdown;
  protected System.Web.UI.HtmlControls.HtmlGenericControl DropdownPanel;
  // structure to store info about a control
  private struct ControlInfo
   public string ID;
   public string Type;
  private void Page_Load(object sender, System.EventArgs e)
  #region Web Form Designer generated code
  override protected void OnInit(EventArgs e)
   // CODEGEN: This call is required by the ASP.NET Web Form Designer.
  private void ShowPersistantControls()
   if (!this.IsPostBack)
    // initialize controls number
    // used to create control id
    Session.Add("LastControl", 1);
    CreatePersistantControl("DropDownList" + Session["LastControl"], "DropDownList");
    Session["LastControl"] = (int)Session["LastControl"] + 1;
    // recreate controls created on previous roundtrips
  private void InitializeComponent()
   this.AddDropdown.Click += new System.EventHandler(this.AddDropdown_Click);
   this.RemoveDropdown.Click += new System.EventHandler(this.RemoveDropdown_Click);
   this.Load += new System.EventHandler(this.Page_Load);
  private void RecreatePersistedControls()
   ArrayList al = (ArrayList)this.Session["DynamicControls"];
   if (al != null)
    foreach(ControlInfo ci in al)
  private Control CreateControl(ControlInfo ci)
   Control ctl = null;
    case "TextBox":
     ctl = new TextBox();
    case "DropDownList":
     ctl = new DropDownList();
   ctl.ID = ci.ID;
   this.DropdownPanel.Controls.Add(new LiteralControl(ctl.ID));
   this.DropdownPanel.Controls.Add(new LiteralControl("<br />" + Environment.NewLine));
   return ctl;
  private ControlInfo PersistControl(string id, string type)
   ControlInfo ci = new ControlInfo();
   ci.ID = id;
   ci.Type = type;
   ArrayList al = (ArrayList)this.Session["DynamicControls"];
   if (al == null)
    al = new ArrayList();
   this.Session["DynamicControls"] = al;
   return ci;
  private void CreatePersistantControl(string id, string type)
   ControlInfo NewControlInfo = new ControlInfo();
   NewControlInfo.ID = id;
   NewControlInfo.Type = type;
   PersistControl(id, type);
  private void AddDropdown_Click(object sender, System.EventArgs e)
   if (Session["LastControl"] == null)
    Session["LastControl"] = 1;
   CreatePersistantControl("DropDownList" + Session["LastControl"], "DropDownList");
   Session["LastControl"] = (int)Session["LastControl"] + 1;
  private void RemoveDropdown_Click(object sender, System.EventArgs e)
   ArrayList al = (ArrayList)this.Session["DynamicControls"];
   ControlCollection cc = DropdownPanel.Controls;
   // if there's at least one control in the DynamicControls session variable,
   // remove the last control
   if (al != null && al.Count > 1 && cc.Count > 1)
    al.RemoveAt(al.Count - 1);
    cc.RemoveAt(DropdownPanel.Controls.Count - 1);
    Session["LastControl"] = (int)Session["LastControl"] - 1;
5/23/2005 9:05:36 PM
asp.net.web-forms 93655 articles. 5 followers. Follow

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