I have a ASP.Net(C#) page. When a user selects a value in dropdownlist, some new controls will be visible to him.
I am able to that now, but the page has to reload every time and state has to be maintained between postbacks.
Is there any way to do the same without reloading of the page in a easiest way possible without using ajax control toolkit?
Additional info: the data for the dropdownlist is coming from the database, and some places it has to be all server side so i can't use javascript .
You can try this idea: http://msdn.microsoft.com/en-us/library/ms178208(v=vs.100).aspx. I have not try it before but it seems logical.
you should go through updatepanel. Put all the controls inside a updatepanel which you want to show on selectedindexchanged event of the dropdownlist and write code behind on selectedindexchanged event of the dropdownlist accordingly. Hope this will help you...
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I have a custom server control (composite control having dynamically created dropdown boxes and textboxes). I have enabled AJAX in order to avoid page reload.The server control is used inside the ASP.NET webcontrol having few buttons which controls the visibility of the server control. Now I enter values in the dropdown box and texboxes and click on any other button. After this postback the last entered values are gone! The control is not remembering the values. Can anyone help me? How can I retain the values after post back?
Ensure that the controls are given the exact same ID after each postback. Also you might want to try initialising your dynamic controls (DropDownList and TextBox) during Page_Init if possible.
If your custom server control is create dynamically all the controls, then you need to recreate them on every post, and you need to create them before the Page_Load(), or else the asp.net cant know them to filled with the post data.
To solve this, if you can not create them before the Page_Load(), then you can fill them by your self with the posted data by using the Request.Form[YourCustomControl.UniqueID] for all controls.
You need to re-create on each postback, see This article
I dynamically load a User Control, with an Update Panel inside a Place Holder.
When I click a button from the User Control, should refresh the Update Panel contents, but it refresh the entire page instead, and the User Control is disappearing from the page, because the page's Page_Load does not load anything if it's a PostBack.
How I can fix it?
Whenever a partial or full postback happen , Automatically all update() method of all updatepanels fire . For preventing such this behavior you need to set UpdateMode="Conditional" property . In this situation you need to specify asynchronous trigger Or ChildrenAsTriggers=true .
for preventing a dynamically loaded-usercontrol to be disappear ,It's good to save it in ViewState , Here is a tutorial and sample application
I think you'll need to reinject the control in page_load or pre_render. Dynamically created controls don't live through postback.
Make sure you are creating the control EVERY page request, regardless of GET/POST. Also, make sure you are giving it the same ID.
I like to override the CreateChildControls method.
You need to add the control page to the page in the page_init method. It has to be added on each post back. The control will retain all the values even after adding it back.
There is a full working example at this link.
I have next situation:
I load dynamic controls during on init, and I do correct initialization.
I add dynamic control before postback
I don't add anything later in load
control is loaded and diplayed correctly
I press postback and nothing happens
Why I really don't know.. I tried everything. So control IS properly initialised. __EVENTTARGET shows the same path as the UniqueId of linkbutton that is firing it. All controls in tree have viewstate=true. So, I really don't know what this is not working.
Any idea? I am desperate.. I don't know.. if anyone could suggest me, if not solution, then just things I should check would be very good.
Is this problem just for this page or do you have other pages on the same site with the same problem?
I am assuming that you have the same problem on all pages.
It could be relate do javascript not being allowed. You could try to add the site to local intranet security are, then refresh the page.
Dynamic controls have to be added back to the control tree on each postback for the events to fire.
Dynamically created controls are not part of their container's viewstate, so setting it to TRUE wouldn't have any effect on the situation and are not evaluated until after the on_init call completes anyways.
I would wrap the logic that is populating these dynamic controls in with a conditional check for a postback if(!IsPostBack)
{ //Insert logic here }
If your dynamic controls take input from the user, or need access to their view state, then you would need to move this call to the Page_Load method as this is the point in the page's lifecycle where viewstate is first evaluated.
I have tow diferent implementations for the same problem.
A gridview that is binded with some data and it has a select column that has a button. When the button click is fired I know in debug that the : sender.SelectedDataKey and sender.SelectedIndex have values that I use later.
But now I whant to use the ajax accordion control. I have an Accordion, and one Pane inside. Inside that pane I have a CollapsiblePanel (that uses the CollapsiblePanelExtender). And in that CollapsiblePanel I have my Gridview.
So, only when I click on the collapsiblePanel I want to get data from DB and bind it to the GridView. But it seems that using this methot the sender.SelectedDataKey and sender.SelectedIndex are Nothing (VB) when the PageIndexChanging fires!
This does not make any sense!
The GridView is the some on both implementations and EnableViewState=true
Thank you.
With the Accordion Panel being an Ajax control, it might be adding the Update Panel in there even though you did not add one to the page. Since the GridView is inside of an Ajax control, all the events that are being triggered by the GridView are going to be captured by Ajax. You might try making the GridView button clicks an Ajax callback as well.
I have run into this problem before where the controls inside of an Ajax Update Panel or an Ajax control; such as the Accordion Panel, fire the server side event handler, but because Ajax is involved, the values were stuck back on the client side.
be sure that your controls are in the same UpdatePanel, or update the various container UpdatePanels.
I've a page that has a series of web controls. One of these is a textbox with AutoPostBack turned off.
The way the page operates is that a button is clicked to save the form data. This button sits outside of the updatepanel.
So when I hit the save button the partial postback happens for the dropdownlist and after this postback has completed a full postback fires for the save button. However when the full postback fires the form data is returned to the state before the save button was clicked - i.e. my changes are removed.
I believe this could be to do with the viewstate being returned from the partial update and that viewstate not updating in the page before the full postback fires - or it getting corrupted.
Does anyone have any ideas?
Thanks.
Don't mean to sound negative but these scenarios are what made me give up "by the book" ASP.net AJAX. Learning jQuery /w simplistic ASP.net forms /w NO postbacks has lead me to build more useful and cooler UI experiences than what I had to battle to get working with update panels etc.
If you set UpdateMode="Conditional" and ChildrenAsTriggers="true" on your UpdatePanel, that will ensure the partial postback only executes when the DropDownList's postback event fires, not when the Button is clicked.
Thanks for the quick response! However I need the save buttons click event to fire too. The order in which the events fire is perfect:
dropdownlist changed event (partial)
save button click event (full)
The problem is the loss of form data after the partial postback.
Many thanks.
I've already posted a solution to this on another post. This simple code will ensure that your viewstate works with both the postback and partial postback.
Ideas for how to deal with viewstate when using ASP.NET AJAX and update panels