We Keep Coding

Dealing with multiple "chained" postbacks from dynamically-created controls in a single page

I'm trying to build a very specific search page for a project and I'm having lot of trouble dealing with multiple postbacks invoked by dynamically-generated controls on a single page.
The page has to work like this:
There is a single checkbox, "Detailed search", that causes a postback on checking/unchecking.
When detailed search is not active, a simple grid with contents and buttons is displayed. Nothing special.
When detailed search is active, N checkboxes must be generated from some dynamic data, that represent the sections where you want the search to happen. Below the checkboxes, an AJAX-enabled tab control will appear, initially with no tab pages.
When checking one of the section checkboxes, a postback will occur. After the postback, data will be searched in the section selected by the user, then a new tab page containing a grid view of results and the name of the section will be added to the tab control. If the checkbox is unchecked, the tab page will disappear from the control, again, after a postback.
Now, the issue is that pretty much everything has to be generated dynamically, and that pretty much everything is connected to something else.
First issue: dealing with the "Detailed search" checkbox. Sounds easy, doesn't it? My initial idea was to set Page.Viewstate["DetailedSearchEnabled"] to true or false during the check/uncheck event handler, then create controls dynamically checking the value of DetailedSearchEnabled during Page_Load.
Nope. The postback event-handling happens between Page_Load and Page_LoadComplete. It would take an additional refresh for things to work as intended.
<< Then I'll just generate the controls on Page_LoadComplete! >>
Nope. Those controls need event handling as well, and if they're generated after Page_Load they will not be wired up correctly.
A possible solution would be generating everything in advance, on Page_Load, and only hiding/showing controls on Page_LoadComplete. But that is inefficient, and one important point of this search page is that only the minimum amount of controls should be generated.
The difficulty of this task seems to come from the way event wiring and the page life cycle work.
Surely there must be a better way of approaching this problem.

First issue: dealing with the "Detailed search" check box.
The correct approach (if you want to use page post-backs) is as follows:
In the CheckChanged event handler, save the value of the Checked property to ViewState["DetailedSearchEnabled"]. If the value is true, add the dynamic check boxes to the page. If the value is false, find and remove them.
Override LoadViewState. After calling base.LoadViewState, re-create the dynamic check boxes and wire up their events if ViewState["DetailedSearchEnabled"] is true. Note that neither Page_Load nor Page_LoadComplete is the appropriate place to do this.
Yes, you should create the dynamic check boxes at two points in the page life cycle. I recommend a helper method.
In general, your event handlers should add or remove just the dynamic controls (if any) affected by those particular events, but LoadViewState should re-create all dynamic controls that existed from the previous page request. You must store enough information in view state for LoadViewState to do so.
My answer to this other question demonstrates how to add and remove dynamic controls. You may want to use it as a reference.

Sounds to me like you should be using a CheckBoxList control to handle your dynamic checkboxes. You can add an remove items to the CheckBoxList during your post back and not have to worry about dynamically adding/removing actual controls/events to the form.
Here is a link to the msdn:
https://msdn.microsoft.com/en-us/library/14atsyf5(v=vs.85).aspx
Here is some sample code:
Protected void Button1_Click (object sender, System.EventArgs e)
{
CheckBoxList.Items.Add(new ListItem("TextValue1", "Value1"));
CheckBoxList.Items.Add(new ListItem("TextValue2", "Value2"));
}

If all else fails, you could still fall back on the quick-and-dirty old-fashioned ASP way.
Use Response.Write or <%...%> to generate your dynamic controls as plain old HTML (simple form fields, e.g. <input type="checkbox" name="foo" value="1" />).
Make sure you have a form field for every piece of information you may need after the postback(s). If necessary, use hidden form fields to 're-post' values across subsequent postbacks.
After postback, retrieve the values of the controls with the Request object.
Use those values to adjust the generation of controls as you see fit.
You should be able to do all of this in Page_Load. The advantage is total freedom. The disadvantage is total freedom to make a big mess of your aspx. So you may want to migrate all this dirty code out of your aspx, and into a custom-made control, which you can then add to your aspx.
When generating your own HTML, be careful not to introduce XSS vulnerabilities. Use HtmlEncode where necessary.

As you suggested yourself, there is a better way to tackle it.
If I was in the same situation, I would create web methods for interacting with the page, and use client side to do the UI. I'm currently working mostly with angular JS, although it does come with a learning curve. You could use ng-hide/ng-show to bind to the checkbox event to display the detailed search. When the n number of checkboxes needs to be displayed, you can then just fill them in with ng-repeat, for each of the items you need to display, after a check/uncheck you can dynamically populate new controls etc. through web method calls if extra data is needed.
Pure ASP postbacks are quite clunky from my experience, and not really suited for building a maintainable dynamic UI.

Instead of making so many postbacks, it would be better to use jquery and ajax calls to load the controls as needed and then attach events to it or you can even use UpdatePnael for that. Help Links:
https://www.simple-talk.com/dotnet/asp.net/ajax-basics-with-jquery-in-asp.net/
http://encosia.com/using-jquery-to-directly-call-aspnet-ajax-page-methods/

ASP.NET Dynamic user controls save data issue

Here is what I have
A set of business entities that resides in the session (for example, Employee:{"Name":string,"Surname":string,"Salary":double, "Position":enum}
A set of user controls (using Telerik.Web.UI), each of it describing a business entity (for example, EmployeeControl.ascx:
RadTextBoxes for Name, Surname and Salary and a RadComboBox for Position. There is also a RadButton in the control, which saves the data that is entered in the controls client-side to a certain entity, which is already known by the time the control is loaded).
A page with a RadTabStrip and RadMultiPage, which is used to render different controls in different tabs
The target RadTab that hosts our Employee control.
So, the issue is: when I hit the Save button, a postback is done, thus clearing my controls and only after that the Click event is fired. I have tried to avoid it by using RadAjaxManager with a OnClientClicking script with canceling the postback, but with no success, because a postback is still generated, although its __EVENTTARGET is RadAjaxManager itself.
Basically, this is what happens:
The user selects a tab with the Employee control with it. The control is filled with initial data on Page_Load. (A postback occurs with re-creating my controls)
The user modifies the data. (Nothing happens, no control generates postback)
The user clicks save. (A postback occurs with re-creating my controls, then a Click event is fired)
No data is saved
When the data is entered again and the save is called, everything is saved as it should.
How can I make this work correctly?
P.S. I was able to achieve the required result (although not completely: the screen "flickers" when a postback is done) by dividing the postbacks into odd ones and even ones (I added another variable in Session named PostCounter, which is incremented every time the page is posted). So, when an expression PostCounter % 2 is equal to 0, I perform another postback by executing __doPostback with its eventTarget parameter being the ClientID of an instance of a RadAjaxManagerProxy, and the argument being just some string that does not match any that is used in my regular Ajax requests.

Make sure your controls always have the same IDs when recreated. Imitating postbacks from other controls should not be needed, the buttons are IPostBack controls so things should work nicely.
This (one AJAX, one full postback) behavior is typical for Sharepoint where you need to add AJAX settings programmatically: http://www.telerik.com/forums/radajaxmanager-in-webpart-on-sharepoint-2010
Also, make sure you do not nest AJAX settings (from a manager and/or proxy), RadAjaxPanels and asp:UpdatePanels: http://www.telerik.com/help/aspnet-ajax/ajax-controls-in-ajaxpanel-and-ajaxsettings.html.

Dynamically add textbox in asp.net

In my page, i got two column and multiple rows. The first column contain the label such as question for the 1st row, and the options for the questions. And the second column is the textboxes. When i click on add button, i wish to add those controls to page which subsequently allowed me to add the value in the texbox to database. I did some research but most of them uses javascript or datatable. Is there any other method?

You don't specifically say what type of .net development you are doing, and your question is tagged with asp-classic, which I doubt you're using. [If you are please please stop] So I will assume you are using Web Forms.
While I don't agree with Inerdial's position that you should avoid dynamic controls at all costs, I will say it does make things much more complex and requires a very good knowledge of the ASP.net Lifecycle. If you truly want to go down that path, here is a great resource.
With that said what you are describing to me does not appear to need that and his suggestion of setting the control visibility to false is a good one.
You could create a row, a panel or a div and output the controls that you need when adding a new row and set it's server-side visibility to false whenever you don't want it displayed. Then you could have a link that when clicked it toggles the visibility to true and will allow the user to add items. Once users add items they'll be displayed in your data table and you can reuse the form to add additional items.
I would also like to encourage you to consider JavaScript if it isn't an overly complex form. It eliminates an extra round-trip to your server and in general is a better user experience.
Edit: This link may also be of use to you.

Is there a way to NOT load a specific control in ASP.NET/C#?

I've a container (RadDockZone - Telerik), and inside it, a textbox field with an "Asp:RequiredFieldValidator", which makes it mandatory. Every time that I work with AJAX operations, the entire container is "reloaded", including the RequiredFieldValidator. This makes the ValidationSummary show the same error message twice, until the page is completely reloaded (I'm using RadAjaxManager to solve the AJAX operations).
So, how can I "don't reload" a specific control (in this case, the RequiredFieldValidator) using C#?
Regards!

If you place the following in page load if(page.Isvalid) the required field validator will be fired once after submitting that form. The message will not be displayed twice.

If you do not include the textbox (or its wrapping containers) in the list of controls updated by the ajax manager, the textbox and the respective required validator should not be updated on ajax requests and the error message should not be visualized.

You should use validation groups. This lets you group all of your validation controls into a group. Then put this same validation group on your submit button and those validation controls will only validate when that particular button is clicked.
Property is assigned on the validation control and button using the ValidationGroup property.
Thomasvdb's suggestion of setting CausesValidation to false also might be a good way to do it.

dynamically generated form how to actually save entered data

i have a form that is generated dynamically.
the plan is to generate it, the user to enter data, and then to save all that lot away.
although a slight variation to this is if the form has previous data associated with it, and then it loads in all pre-populated. - the user may then change any previous selections.
and that is the rub really, i know if i call generateform regardless of postback the viewstate should take over and remember what the settings weer.. but as the generateform method as mentioned above populates the form if the form has previously been saved. which will win, the viewstate or the generateform method for the field populations.. ?
thanks
nat

If you dynamically generate any form controls that post data or cause a postback, you need to recreate them again on postback in order for them to be bound to their data, or their events, after the postback. Conceptually, this makes sense. If you don't have a control in your form after the postback, how could you look at its contents?
There are several ways you could approach this problem.
1) Call GenerateForm() no matter what. Since you said it pre-populates some of the data, you would need to change it so it can be called without doing that. ASP.NET will populate the controls with the data posted automatically on postback, which is what you want.
2) Keep a list of all your dynamically generated controls in a ViewState variable, so you can re-generate them upon postback. For most situations involving dynamically-created controls that aren't very simple (e.g., you may not know in advance exactly what controls are generated), this is the best solution. And often you will want to be able to access the data after a postback, but maybe you really don't want to recreate the whole form because you aren't using it any more.
As long as you recreate a control of the same type and ID on or before Page_Load(), it will be bound to the posted data. It does not need to be in exactly the same place on your form. And it does not need to be used or displayed, either - you can destroy it before the form is rendered, e.g., in Page_PreRender()
3) If you have no interest in any of this, you can always use Request.Form to look directly at the posted data, though this can also be tricky because the names will likely not match your form control IDs exactly. ASP.NET generates unique client-side IDs that depend on the container, and this is what you'll find in Request.Form. If you don't regenerate a control, you may not be able to easily determine the ID that you are looking for. Generally, you should not do this, but it's a way to look at the posted data and sometimes you need it.