Solved

ASP.NET C# - Dynamically adding table rows & cells issue.

Posted on 2009-07-01
7
5,969 Views
Last Modified: 2013-12-17
I'm trying to click a linkbutton and have more rows added to a table via server side code. I will adding controls that I can iterate through later.  Every time the link button it clicked, I want another NEW row to be added.  However, when clicked...  one new row is added, but that's it. When clicked again, it seems that the row is that is just added is lost and the same row is re-added.   ViewState not being enabled doesn't seem to be the problem, as I have it enabled ever where I can think of.  Maybe my understanding of how postback and viewstate works is incorrect. I would expect that when you have a session on the server and viewstate enabled that when a control is dynamically added via postback, it would persist until you leave the page.  Anyone have any ideas? I'm sure someone has come across this before.
<%@ Page Language="C#" EnableViewState="true" EnableSessionState="True" AutoEventWireup="true" CodeFile="ajaxtest.aspx.cs" Inherits="ajaxtest" %>
 
<!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>Untitled Page</title>
</head>
<body>
    
    <form id="form1" runat="server" enableviewstate="true">
  
        <asp:LinkButton ID="LinkButton1" runat="server" onclick="LinkButton1_Click">LinkButton</asp:LinkButton>
        <asp:Table runat="server" ID="MyTable" EnableViewState="true">
            <asp:TableRow>
                <asp:TableCell>
                Exsisting Row
                </asp:TableCell>
            </asp:TableRow>
        </asp:Table>
        
        
    
    </form>
</body>
</html>
 
 
using System;
using System.Collections;
using System.Configuration;
using System.Data;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.HtmlControls;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
 
public partial class ajaxtest : System.Web.UI.Page
{    
    int Counter = 0;
 
    protected void Page_Load(object sender, EventArgs e)
    {
        
 
    }
 
    protected void LinkButton1_Click(object sender, EventArgs e)
    {
        TableCell NewCell = new TableCell();
        TableRow NewRow = new TableRow();
 
        Counter++; 
        NewCell.Text = "Dynamically Added " + Counter.ToString();
        
        NewRow.Cells.Add(NewCell);
        MyTable.Rows.Add(NewRow);
    }
}

Open in new window

0
Comment
Question by:orrsafety
[X]
Welcome to Experts Exchange

Add your voice to the tech community where 5M+ people just like you are talking about what matters.

  • Help others & share knowledge
  • Earn cash & points
  • Learn & ask questions
  • 4
  • 2
7 Comments
 
LVL 40

Expert Comment

by:Kyle Abrahams
ID: 24754965
After the rows.Add

MyTable.DataBind();

DataBind syncs up the changes.
0
 

Author Comment

by:orrsafety
ID: 24755029
I gave that a shot, but that didn't do it. I'm still only getting one new row. Also to clarify, this is not a "gridview" and I'm not working with any data that's getting bound.  Thanks for time and suggestion.
0
 

Author Comment

by:orrsafety
ID: 24755124
I'm working with the .net 2.0 framework, I tried with 3.5 as well and I'm still getting the same issue.  Don't know if that helps?
0
Independent Software Vendors: We Want Your Opinion

We value your feedback.

Take our survey and automatically be enter to win anyone of the following:
Yeti Cooler, Amazon eGift Card, and Movie eGift Card!

 
LVL 13

Accepted Solution

by:
crazyman earned 500 total points
ID: 24755365
Dynamically created controls must be re-created on each postback see : http://www.singingeels.com/Articles/Dynamically_Created_Controls_in_ASPNET.aspx

Since you add the table row and then next postback you dont re-add the one you already added, it wont get re-created.

You could create list held in view state, something like :

public List<string> Items
{
                get {return this.ViewState["Items"] ?? new List<string>();
                set {this.ViewState["Items"] = value;
}

then in your button click do something like

List<string> lst = this.Items;
lst.Add("New Item");
this.Items = lst;

then override CreateChildControls and do something like

foreach (string str in this.Items)
{
TableCell NewCell = new TableCell();
        TableRow NewRow = new TableRow();
        NewCell.Text = String.Format("Added Cell {0}",str);        
        NewRow.Cells.Add(NewCell);
        MyTable.Rows.Add(NewRow);

}
0
 
LVL 13

Expert Comment

by:crazyman
ID: 24755527
This works ok for me

<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
    <title></title>
</head>
<body>
    <form id="form1" runat="server">
    <asp:LinkButton ID="LinkButton1" runat="server" onclick="LinkButton1_Click">LinkButton</asp:LinkButton>
        <asp:Table runat="server" ID="MyTable" EnableViewState="true">
            <asp:TableRow>
                <asp:TableCell>
                Exsisting Row
                </asp:TableCell>
            </asp:TableRow>
        </asp:Table>
 
    </form>
</body>
</html>
=============================================================CODEBEHIND
 
using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
 
public partial class Test : System.Web.UI.Page
{
    public List<string> Items
    {
        get { return (List<string>)this.ViewState["Items"] ?? new List<string>(); }
        set {this.ViewState["Items"] = value;}
    }
 
    protected void LinkButton1_Click(object sender, EventArgs e)
    {
        string txt = DateTime.Now.ToString();
        List<string> lst = this.Items;
        lst.Add(txt);
        this.Items = lst;
        RenderTableItem(txt);
 
    }
 
    protected override void CreateChildControls()
    {
        //Save any existing that were added via markup
        RenderTable();
    }
 
    private void RenderTable()
    {
        foreach (string str in this.Items)
        {
            RenderTableItem(str);
        }
    }
    private void RenderTableItem(string str)
    {
        TableCell NewCell = new TableCell();
        TableRow NewRow = new TableRow();
        NewCell.Text = String.Format("Added Cell {0}", str);
        NewRow.Cells.Add(NewCell);
        MyTable.Rows.Add(NewRow);
    }
 
}

Open in new window

0
 

Author Comment

by:orrsafety
ID: 24755717
Well I think this certainly puts me on the right track.  I wasn't aware of that process.  Thank you very much!
0
 

Author Comment

by:orrsafety
ID: 24755929
Since I was only concerned with a single table. This is what I ended up doing.  I saved the table to a session variable session variable which is nice cause it saves everything in the table. I set a temp table to the session saved table or if that doesn't exists to the table on the page. I make all the modifications to that, then place it back in the page and save to the session variable. This works exactly like I wanted it to.
<%@ Page Language="C#" AutoEventWireup="true"  CodeFile="Default.aspx.cs" Inherits="_Default" %>
 
<!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>Untitled Page</title>
</head>
<body>
    <form id="form1" runat="server">
    <div>
        <asp:LinkButton ID="LinkButton1" runat="server" onclick="LinkButton1_Click">LinkButton</asp:LinkButton>
        
        <asp:Panel ID="TableContainer" runat="server">
            <asp:Table ID="TableOnThePage" runat="server">
                <asp:TableRow>
                    <asp:TableCell>Exsisting Row</asp:TableCell>
                </asp:TableRow>
            </asp:Table>
        </asp:Panel>
    </div>
    </form>
</body>
</html>
 
=====================================================================
 
using System;
using System.Configuration;
using System.Data;
using System.Linq;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.HtmlControls;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Xml.Linq;
 
public partial class _Default : System.Web.UI.Page 
{
    
    protected void Page_Load(object sender, EventArgs e)
    {
        if (IsPostBack)
        {
            if (Session["PersistentTable"] != null)
            {
                TableContainer.Controls.Remove(TableOnThePage);
                TableContainer.Controls.Add((Table)Session["PersistentTable"]);
            }
        }
        else
        {
            if (Session["PersistentTable"] != null) Session["PersistentTable"] = null;
        }
    }
 
    protected void LinkButton1_Click(object sender, EventArgs e)
    {
        Table TempTable = new Table();
        if (Session["PersistentTable"] != null) TempTable = (Table)Session["PersistentTable"];
        else TempTable = TableOnThePage; 
        
 
        TableCell NewCell = new TableCell();
        TableRow NewRow = new TableRow();
 
        NewCell.Text = "Dynamically Added " + TempTable.Rows.Count.ToString();
 
        NewRow.Cells.Add(NewCell);
        TempTable.Rows.Add(NewRow);
 
        TableContainer.Controls.Remove(TableOnThePage);
        TableContainer.Controls.Add(TempTable);
        Session["PersistentTable"] = TempTable;
        
    }
}

Open in new window

0

Featured Post

Secure Your Active Directory - April 20, 2017

Active Directory plays a critical role in your company’s IT infrastructure and keeping it secure in today’s hacker-infested world is a must.
Microsoft published 300+ pages of guidance, but who has the time, money, and resources to implement? Register now to find an easier way.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

Suggested Solutions

A long time ago (May 2011), I have written an article showing you how to create a DLL using Visual Studio 2005 to be hosted in SQL Server 2005. That was valid at that time and it is still valid if you are still using these versions. You can still re…
This article aims to explain the working of CircularLogArchiver. This tool was designed to solve the buildup of log file in cases where systems do not support circular logging or where circular logging is not enabled
With Secure Portal Encryption, the recipient is sent a link to their email address directing them to the email laundry delivery page. From there, the recipient will be required to enter a user name and password to enter the page. Once the recipient …
A short tutorial showing how to set up an email signature in Outlook on the Web (previously known as OWA). For free email signatures designs, visit https://www.mail-signatures.com/articles/signature-templates/?sts=6651 If you want to manage em…

763 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question