Well I've got some textboxes dinamically created in a .cs file and I want to save/store their values when I click on Update button in a detailsview's edit mode, so I've got seted button's onclick event to a function to do this.
The problem is that the postback event occurs before the "OnClick" event, and then the textboxes' values are lost.
How can I save/store their values first?.
Please, help me with this.
Thanks in advance!
You can detect the page's first loading or post back(OnClick, SelectedItemIndexChanged like..) with the Page.IsPostBack property.
You should check this property value in the Page_Laoad event handler.
It helps to understand the ASP.NET page life cycle.(See here for more info.)
Basic events are as follows:
PreInit
Init
PreLoad
Load (controls are filled with postback values here)
Control events (OnClick happens here)
PreRender
Render
Unload
Usually during the "Init" event you want to create all of the controls, including any dynamic controls for the user.
During the Load event asp.net copies all of the post date back from the client to the controls in the page. But in order for this to work on the postback the same controls that were created on the initial render must exist in the same order with the same IDs.
Then in PreRender you can change the page state including adding and removing controls for the next post.
So to clarify here's how I would imagine your page flow:
OnInit - Construct your controls and populate with the initial values.
OnLoad - During postback your control will be populated with the users updated values.
OnClick - Use the event of the user's button click to then save the updated values.
Related
I am using a ajaxToolkit:AsyncFileUpload that allows the user to upload a excel file. In the AsyncFileUpload1_UploadComplete() event, I am reading the excel data and creating excel structure using div and adding to the page. But these dynamically created controls are not being added to the page. I added a button in the updatepanel and checked. On button click event, I created same above controls. In this case, the controls are rendering to the page. The controls are not rendering in case of ajaxToolkit:AsyncFileUpload only. Can anybody please tell me what is the fix for this.
Add Button into UpdatePanel where you want to show new controls and make it invisible with css style.
In the AsyncFileUpload1_UploadComplete server-side method, save your data to Session state.
In the client-side OnClientUploadComplete event handler call __doPostBack function with hidden button's UniqueID first parameter value. Then make all stuff required to render dynamic content in that button's click handler.
This old chestnut again.
My page is constructed as follows; I have a dropdownlist which is databound on first load. When the user selects a value from this, a postback is performed which then databinds a repeater control.
The ItemTemplate of this repeater control contains a placeholder control. In code behind in the ItemDataBound event of the repeater, I am adding two controls dynamically to this placeholder, a hiddenfield and a checkbox.
When the user clicks the save button, I then want to iterate over all those dynamically created hiddenfields and checkboxes and determine their values. However when the user clicks the save button, those controls no longer exist as shown in the page trace.
I know this is a lifecycle issue and the articles I've seen on this suggest using Init methods to dynamically create your controls but I can't because of the way my page works, e.g. the repeater control only appears and binds after a value is chosen from the dropdownlist.
What do I need to do to maintain the dynamic controls through the postback caused by clicking on the save button?
The problem is when you hit the save button probabily you dont re-bind the repeater and the controls you have added at run time withint the ItemDataBound event are not longer available(because they don't exist anymore)
Why don't you add those control at design time using the Eval function the set up the value of the hidden field?
You just don't create them dynamically just on the on selection change of the drop-down set visibility true or false for the repeater that will solve your problem.on post back you have to again create those control as they are Dynamically created.
I am creating some textboxes dynamically and I try to get their values when I click a button, but they are gone. I create the text boxes (declaration, initialization, adding them to the place holder) in another click button event. What shall I change to be able to read their values?
If you will create the controls on the Init stage (eg: Init event) on every request (eg, both postback and non-postback) then they will be available and will preserve their state.
There could be several reasons one of Them being your control initialization being executed prior to the event handler. This will be the case if you on post back initialize the controls in page_load. The click event handler is executed after page_load is run
How about getting the values using a simple Request.Form. That should work regardless of how you add the controls. Post some source, so we can see what's going on. :)
I want to make use of "complex" usercontrols with more than one control element within. It's the same control I will reuse in the list, and I have a PlaceHolder control for it already.
I can add the control with LoadControl(path to .ascx) - no problem.
I can through my custom properties get/set access the embedded Labels, too, so I can initialize each control perfectly.
But when adding LinkButtons, I get into trouble/problems.
When I click the button, I do get a "submit" of the page rendering the controls; but the control's own button event does not seem to fire (or at least PageLoad on the parent page seems to fire first?) - I can't figure out where my event goes or where to look for a name/ID or parameter for this button.
How come or what am I doing wrong here?
I've made a "fake button" now by using a label more with a "hardcoded A HREF" with an ID in the URL, but I would like to learn what event I need to catch and where or how to init the button, because I want to be able to use "default ASP.NET" controls for these usercontrols (hopefully without too much patchwork-coding)...
The only reason that events get "lost" is because your controls are not being recreated in such a manner that ASP.Net can associate the event with the control after the postback. It does so through the use of the ID property.
In other words, you're doing one of three things wrong:
1) You're assigning the ID's of your linkbuttons differently during the creating phase in Init after the postback
2) You're creating your linkbuttons dynamically using code, but you're doing it after the Init phase of the page lifecycle, so that your controls do not participate in ViewState.
3) You're re-binding the datasource of the parent control containing the linkbuttons on every postback. Use if (!IsPostBack) to prevent rebinding it every time.
Without seeing your code I can't give anything more specific than that unfortunately.
I have button Add and Remove on my page.
Add button adds one checkbox, two textboxes and one dropdownlist to a new line on my page.
Remove button removes them.
I have this running nicely by following Joe Stagner's example.
Problem:
The controls that are created dynamically all need to fire the same event when checked (for checkboxes), also for selected index changes (for dropdownlists).
I have tried to add event handler when I create an object but it doesn't seem to fire?
you need to persist the dynamically created controls in some way [session, viewstate, etc.] for each page load. Recreate the dynamic controls and re-bind the events using delegates on each page load in preInit function.
I think you're probably running into the fact that your page, upon each page post, is being completely recreated - essentially the page has to duplicate what controls were on your page before it can attempt to feed postback (and events) to them. I think what you probably need to do is add code to your page_load which will re-create the dynamically created controls, with the same ids as they had, and register the event handler.
Sounds like you have a page life cycle issue.
For a dynamically created controls to fire events you should create them in the PreInit event of the page.
Here's a link to a cheat sheet for Asp.net page life cycle.
yeah,
like what all said, it is Life cycle issue.
when you load user controls dynamically you should always do the following.
Assign a unique ID for each User Control.
Reload the user controls on Page_Load or Page_Init Events.
and to make it all easier i suggest to abstract the loading to a function that you will call from Page_Load and Page_Init as mentioned before, this function will check if hte target user control was loaded and will load it again for you, to do that, you store the loaded user controls IDs in Session or viewstate.
hope this helps.
If you want to do it without auto post back you can remove the auto post back and throw and ASP button on there. Any runat server should fire off your dynamic event handlers.