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adding user controls programatically to an updatepanel

In my asp.net application, I need to be able to dynamically add user controls based on data in a database.
For example, on page1, I will bind three elements to a repeater:
some html content
a user control
more html content.
The repeater on the page is surrounded by an updatepanel
(updatemode=conditional, childrenastriggers=false)
The user control also has it's own updatepanet
(updatemode=conditional, childrenastriggers=true)
So, what I have is something like this:
outer update panel<br/>
repeater<br/>
item 1 = html<br/>
item 2 = user control<br/>
user control update panel<br/>
user control content<br/>
/user control update panel<br/>
item 3 = html<br/>
/repeater<br/>
/outer update panel<br/>
The problem is, I don't get any events fired by my user control. I'm pretty sure I need to create the control in the page_init, but I'm a little unsure of how to do this, since I may have to create any number of user controls of different types, and place them at different locations on the page. Has anyone ever run into this problem before, and how did you solve it?

Steps
Add add a placeholder control to updatepanel.
In CS file create a instance of your usercontrol.
Add that control to placeholder.

Dynamically Created User Control's Dropbox Items from Database resets on postback

First off, I have managed to create a web application where my dynamically created user controls are recreated and repopulated with the correct information upon postback. I am not sure what my problem is, but i hope that you will be able to help me figure it out based on my situation:
On my page i enter the number of controls to be created into a hardcoded textbox (its on the aspx page) and click the okay butten. This in turn, creates the specified number of user controls dynamically using c# in the background.
So far the desired number of dynamic controls are in a table on the page.
Next...
I have 1 textbox and 4 dropboxes on each dynamic user control. When i type a company name into the textbox field and press enter or click away (on text changed event) it autoposts back and the textbox retains the company name that i have typed in.
Based on this string the dropboxes are populated from the database. Now when i select the desired items from the dropboxes and click on the save button (located outside of the dynamic controls, on the page) it does an insert to the database, but it turns out that upon this postback the indexes from the dropboxes have been reset and the wrong values get inserted.
The following pictures show firstly, how it should be and then how it is.
Basically the company name remains in the textbox of the dynamic control, but the information i choose from the dropbox resets to the first index.

It's hard to tell what happend without code, but this is a common mistake:
If you fill/create the dropdownlist controls in the page load event and you post back, the code will refill/recreate the controls. That's why you have to use something like If(!IsPostBack) in your page load event. Otherwise it will execute that code everytime you do a postback and actually just want to execute the code in your event handler for that button.

If you're dynamically creating the controls, make sure to do that in the Page_Init event. Dynamic controls have to be recreated on every postback. Their state is restored after the Page_Init (if it is a postback), so make sure to only set their values in Page_Load if you want to overwrite them.

How to append controls to a panel?

I am developing a dynamic website in ASP.NET. As a trial I tried a code shown below, that adds some controls to Panel1. When user clicks a button for the first time the controls are added to the Panel but when user clicks the same button for second time, the previous controls are replaced with new ones. But I want the controls to be appended one after the other each time the user clicks the button. The code is something like this:
Control c=Page.LoadControl("DData.ascx");
Panel1.Controls.Add(c);
I also tried
Control c=Page.LoadControl("DData.ascx");
Panel1.Controls.AddAt(Panel1.Controls.Count,c);
But this replaces the first output. Please tell me how to append these controls?

As you would expect, this appends a single control:
Control c = Page.LoadControl("DData.ascx");
Panel1.Controls.Add(c);
You can append as many controls as you wish in this fashion.
However, you need to keep track of the controls you are adding in some persisted/stateful fashion (database, Session, ViewState, etc.).
You need to rebuild the control tree every time the page loads.
See my answers to similar questions:
https://stackoverflow.com/a/10050755/453277
https://stackoverflow.com/a/9545079/453277

It may be about the life cycle of asp.net page. Each time when page loads it returns to the initial state. Button Click events are handled after page load and you have only one control at the page. Please look Button to dynamically add controls everytime it's clicked

Dynamic Drop Down List ASP.net

How can I create a dynamic drop down list without using AutoPostBack. I ask because I just want to change the value of what the second drop down list displays and then the user clicks a button and it submits. But If I use AutoPostBack then it postbacks to page and runs code that shouldn't be run until that final box has been selected. (I use Postback in the other part of my program so using !IsPostBack isnt a option.) I looked at Javascript but ASP generates all of its controls names at runtime. What can I do? I have looked at the Ajax CascadingDropDown control but my problem with that is it contained in a XML file or a Database, I need this to be contained inside my Page. Any Ideas?

You can use the CascadingDropDown control from the AJAX Control Toolkit

Maybe this example will help? It's part of the ASP.NET AJAX Control Toolkit available here.

You can use AJAX to get the values for the second drop down list, based on the selected value of the first. Add a onchange event handler on the client-side to the first drop down list that makes the AJAX call and fills the second on success.

UserControl - accessing textbox within UserControl within a web form

I am using c#.net
I have different views within my webform, these all generally display different information except for three textboxes (arrival / seen / depart time). To try and cut down on code, I have created a UserControl which contains these three textboxes.
I have referenced the UserControl at the top of my webform and also within each view.
<%#Register TagPrefix="uc1" TagName="userTimes" Src="~/usercontrols/userTimes.ascx"%>
<uc1:userTimes id="userAppointmentTimes" runat="server"></uc2:userTimes>
can’t seem to access the textboxes from the code behind. I need to firstly populate the textboxes and also hold any updated information to be re-inserted back into the database if changed.
Also each textbox has two Validation controls:
First makes sure it is in time
format HH:MM
Second makes sure the arrival is
before the seen time etc
My two questions are:
How do I access the UserControl from
the code behind? I have read that I
need to use the FindControl but I
don’t understand why, when I know
what it is called.
Do I undertake the validation
(server side) within the UserControl
code behind or the webform code
behind?
Thanks in advance for any help.
Clare

1.) You can access the User Control by its ID from the page's code behind - userAppointmentTimes in your case. To access your TextBoxes within the webform you need to use the FindControl-Method at the User Control level. So something like userAppointmentTimes.FindControl("WhateverTextBoxID") should work. You need to cast the result to TextBox of course.
You can't access the text boxes because ASP.Net does not automatically expose them for you. So alternatively you can provide public properties to set/get values to/from your textboxes inside your user control.
Within the user control, you can access your textboxes by their IDs.
2.) Put the validation controls inside your user control.
By webform you mean it's all inside the asp.net form-tag or do you have an asp.net form like FormView nested inside? If the latter is true you need to use FindControl at the FormView level - formView.FindControl("userAppointmentTimes"). Otherwise the user control is accessible from page level via its ID.