FAQ - Frequently Asked Questions

Re: Solution to the FindControl problem

aplon — Wed, 28 Oct 2009 11:46:35 GMT

Hey Guys, I am going CRAZY with this FindControl stuff. Any help will be GREATLY appreciated. This is the scenario:

I am using the whole membership login stuff described in the tutorial (GREAT STUFF, btw)
I have a master page with a LoginView1 which includes 2 Labels
I have a content page from which I do the Login with the LoginWizard
Once the user is authenticated, I want to place the user's role in one of the Master's Label box described in step 2
I have tried all recomendations: FindControlIterative, using several FindControls in one sentence, etc.
Example: "

lblUserType = Page.Master.FindControl("LoginContent").FindControl("LoginView1").FindControl("lblLoginUserRole")"

As you can see, the Label is contained inside the LoginView, which in turn is contained inside a ContentPlaceholder which is located in the Master page.

I am goin crazy with this as I continue to get an error message that states: "Object reference not set to an instance of an object"

I also tried setting up the property in the Master page, but I cannot reference the Label control either.

Please...please, any help will do!!!!

Thanks a lot, Ariel

I need this script plz helppp

LeonardSelmani — Sat, 24 Oct 2009 02:31:02 GMT

I need this script plz helppp

Script is like this web : merrjep.com plz help to find iii need soo much

Re: Solution to the FindControl problem

friendster — Thu, 17 Sep 2009 09:21:05 GMT

This one is intresting.

http://highoncoding.com/Articles/606_Creating_a_BetterFindControl_and_MuchBetterFindControl.aspx

Raj

Re: Solution to the FindControl problem

SugarBomb — Wed, 16 Sep 2009 15:38:30 GMT

david wendelken:

chalamarc:

i think using of findcontrol() on your formview or anyother control name, it is the best way as you neednot to actually go down on your performance and also you can get rid of all the code that has been shown on the top and one which make full use of the api's and its functions which microsoft provides.

If that were a valid argument, we would still be coding in COBOL and FORTRAN, or maybe 1s and 0s. :)

Computer Science is the science of giving away something you want to get something else you want more.

Which route to use is simply a matter of priorities. The recursive (or iterative) versions of FindControl provide the following benefits and drawbacks:

- Runtime Performance
+ Codetime Performance (it's faster and more convenient for the programmer!)
+ Robustness when the number of levels in the UI Layer changes
+ Easier code to read.

Hard-wiring the reference by nesting chaining FindControl methods offers the following benefits and drawbacks:

+ Runtime Performance
- Codetime Performance
- Robustness
- Harder to read.

Pick the method that best meets your needs.

I hope that a lot of people stumble cross this bit of wisdom. If Codetime performance was properly considered in code construction, coding efforts would move closer to projected timelines.

I have found through years of experience in managing coding efforts (including my own) that professional developers err more on the side of optimizing RunTime performance vs CodeTime performance.

You also could express the "Robustness" and "Harder to Read" jointly as "BugTime" and "MaintenanceTime" performance. These are huge time investments.

Re: Solution to the FindControl problem

disearches — Thu, 06 Aug 2009 15:22:36 GMT

for data presentation contols, you have to use the findcontrol on the individual rows or items (depending on the kind of control)

for example for a listview control : listview1.items[0].findcontol();

for a gridview: gridview1.rows[0].findcontrol();

i have tried it and it worked

Re: Solution to the FindControl problem

the_N_Channel — Thu, 06 Aug 2009 02:09:25 GMT

Got a solution. This was because the control was not explicitly being created without the FormView being data bound. I needed to explicitly call Formview1.DataBind(). I also didn't understand that the ItemTemplate is only rendered when the data source actually has data, otherwise the EmptyDataTemplate is used.

For FindControl() in naming containers with templates involved, it's important to know if your template is being created and your controls exist when you think they do.

Re: Solution to the FindControl problem

the_N_Channel — Thu, 06 Aug 2009 00:03:00 GMT

I echo that sentiment. I've gone over dozens of threads that talk about using FindControl in Pre_Render(), Data_Bound(), and a whole bunch of other places, and this still doesn't work.

<%@ Page Title="" Language="C#" MasterPageFile="~/Site.master" AutoEventWireup="true" CodeFile="Default2.aspx.cs" Inherits="Default2" %>

<asp:Content ID="Content1" ContentPlaceHolderID="ContentPlaceHolder1" Runat="Server">

<asp:FormView ID="FormView1" runat="server" onprerender="FormView1_PreRender">

<asp:TextBox ID="TextBox1" runat="server"></asp:TextBox>

</ItemTemplate>

</asp:FormView>

</asp:Content>

<%@ Page Title="" Language="C#" MasterPageFile="~/Site.master" AutoEventWireup="true" CodeFile="Default2.aspx.cs" Inherits="Default2" %>

<asp:Content ID="Content1" ContentPlaceHolderID="ContentPlaceHolder1" Runat="Server">

<asp:FormView ID="FormView1" runat="server" onprerender="FormView1_PreRender">

<asp:TextBox ID="TextBox1" runat="server"></asp:TextBox>

</ItemTemplate>

</asp:FormView>

</asp:Content>

using System;

using System.Collections.Generic;

using System.Linq;

using System.Web;

using System.Web.UI;

using System.Web.UI.WebControls;

public partial class Default2 : System.Web.UI.Page

{

protected void FormView1_ItemCreated(object sender, EventArgs e)

{

TextBox aText = (TextBox) Util.FindControl("TextBox1", Page.Controls);

TextBox myText = (TextBox)FormView1.FindControl("TextBox1");

myText.Text = "Hello!";

}

protected void FormView1_DataBound(object sender, EventArgs e)

{

TextBox myText = (TextBox)FormView1.FindControl("TextBox1");

myText.Text = "Hello!";

}

protected void FormView1_PreRender(object sender, EventArgs e)

{

TextBox myText = (TextBox)FormView1.FindControl("TextBox1");

myText.Text = "Hello!";

}

No matter where I try, FindControl is returning null. I'm also running 3.5 SP1. I have a hard time believing its the framework itself, but none of the solutions I've seen posted on the forums seem to work.

Re: Solution to the FindControl problem

disearches — Wed, 05 Aug 2009 10:03:52 GMT

Hi guys please i have read thru all the replies in this topic and i have tried most of em, but i still cant get the controls embeded in Data controls like gridview , datalist, formview etc.

this is an old post (early replies were based on .NET 2.0), i am on .NET 3.5 SP1, i dont know if they is any bug in this current framework thats resulting to my problem.

Re: Solution to the FindControl problem

david wendelken — Mon, 23 Feb 2009 05:46:45 GMT

It is simply that a recursive FindControl has to do more work than a FindControl that goes directly to where the object is on the page.

More work equals "takes longer".

That said, "takes longer" isn't very much longer! I've never noticed any difference in run-time performance.

If I had an application with 10,000 people using it all day long, I suspect I might notice the difference.

So, if you have a lot of users who are on the system all the time, you might want to spend the programming time to give the findcontrol routine a better starting point. If it's a page that does not put that type of load on the system, save your employer the programming time. It costs more than the cpu cycles.

Re: Solution to the FindControl problem

mhlove — Mon, 23 Feb 2009 04:15:39 GMT

tysonh28, thanks for your comments on "Solution to the FindControl problem". I am not so much a newbee, but I am still learning... Can you expand on your comments about recursive FindControl? I want to understand why it's not good to use. I do asp.net (vb) pages for a call center. I am working on a project and I will need top preformance. I do not what to do anything to take away form that... Thanks in advance. MhLove

Re: Solution to the FindControl problem

sirdneo — Wed, 17 Dec 2008 11:08:58 GMT

Recursive Methods really degrates the performance of system and I belive that FindControl is also a very heavy operation itself.

Is there any alternate which is lot more faster than this approach.

Re: Solution to the FindControl problem

ayanb — Tue, 05 Aug 2008 13:15:45 GMT

thanks for the code it helps me a lot

Re: Solution to the FindControl problem

Yankee — Thu, 26 Jun 2008 20:44:04 GMT

Here is all you need to find all the nested controls (including their names) in a page:

private void FindAllControls(ControlCollection controls, int depth)

{

foreach (Control control in controls)

{

// Use the depth parameter to indent the control tree.

Response.Write(new String('-', depth * 4) + "> ");

// Display this control.

Response.Write(control.GetType().ToString() + " - <b>" + control.ID + "</b><br />");if (control.Controls != null)

{

FindAllControls(control.Controls, depth + 1);

}

Usage:

protected void Button1_Click(object sender, EventArgs e)

{

FindAllControls(Page.Controls, 0);

}

So for a webpage like this:

<body>

<asp:SqlDataSource ID="SqlDataSource1" runat="server" ConnectionString="<%$ ConnectionStrings:Anunturi %>"

SelectCommand="SELECT * FROM [Anunturi]"></asp:SqlDataSource>

<asp:FormView ID="FormView1" runat="server" DataKeyNames="ID"

DataSourceID="SqlDataSource1">

ID:

<asp:Label ID="IDLabel" runat="server" Text='<%# Eval("ID") %>' />

<br />

Title:

<asp:Label ID="TitleLabel" runat="server" Text='<%# Bind("Title") %>' />

<br />

Category:

<asp:Label ID="CategoryLabel" runat="server" Text='<%# Bind("Category") %>' />

<br />

</ItemTemplate>

</asp:FormView>

<br />

<asp:Button ID="Button1" runat="server" OnClick="Button1_Click" Text="Button" />

</form>

</body>

Your test will end up like this:

> System.Web.UI.LiteralControl -
> System.Web.UI.HtmlControls.HtmlHead -
----> System.Web.UI.HtmlControls.HtmlTitle -
> System.Web.UI.LiteralControl -
> System.Web.UI.HtmlControls.HtmlForm - form1
----> System.Web.UI.LiteralControl -
----> System.Web.UI.WebControls.SqlDataSource - SqlDataSource1
----> System.Web.UI.LiteralControl -
----> System.Web.UI.WebControls.FormView - FormView1
--------> System.Web.UI.WebControls.ChildTable -
------------> System.Web.UI.WebControls.FormViewRow -
----------------> System.Web.UI.WebControls.TableCell -
------------> System.Web.UI.WebControls.FormViewRow -
----------------> System.Web.UI.WebControls.TableCell -
--------------------> System.Web.UI.LiteralControl -
--------------------> System.Web.UI.WebControls.Label - IDLabel
--------------------> System.Web.UI.LiteralControl -
--------------------> System.Web.UI.WebControls.Label - TitleLabel
--------------------> System.Web.UI.LiteralControl -
--------------------> System.Web.UI.WebControls.Label - CategoryLabel
--------------------> System.Web.UI.LiteralControl -
------------> System.Web.UI.WebControls.FormViewRow -
----------------> System.Web.UI.WebControls.TableCell -
----> System.Web.UI.LiteralControl -
----> System.Web.UI.WebControls.Button - Button1
----> System.Web.UI.LiteralControl -
> System.Web.UI.LiteralControl -

So now you can access a nested control (e.g. TitleLabel) like this:

Label Label1 = Page.FindControl("FormView1").FindControl("TitleLabel") as Label;

I hope you find this useful!

Good luck!

Re: Solution to the FindControl problem

CaptainStarbuck — Tue, 29 Apr 2008 21:52:14 GMT

Unless you're creating controls dynamically that you need to find later, or you're drilling into a grid that's populated with a datasource, might it be useful to iterate once when a page is first built, and store some of that information in state? Where would the best place be to intercept the page build: Application_PreSendContent? Page_Unload? Has anyone done this?

Re: Solution to the FindControl problem

izeman — Tue, 15 Apr 2008 11:47:36 GMT

Hi ks2007

It may be to late now but here it goes.

You can write a helper class witch contains the FindControl method then in code behind you do the following:

//Invoke a new instance of your helper class
FindControls findControl = new FindControls();

this assumes that your helper class is named FindControls.

then you simply in stead of running FinControl() framework method you run following

Label label= findControl.FindControlByID(Page.Controls, "ControlName") as Label;

findControl = new instance of your helper class

FindControlByID(Page.Controls, "ControlName") = the method in your helper class

now you have a "new" label control in you code behind called label... you can use it like this.

label1.Text = label.Text; ...just like any other label control in your app.