I have a repeater control that pulls back some data from a database and creates a radiobuttonlist for values related to each row. I don't know how many rows will be coming back, so I don't know how many radiobuttonlists there will be. This repeater is inside of a form, and once I click "Submit" on the form I need to get the values from the radiobuttons generated by the repeater.
Any thoughts on how to do this?
There are a few options.
One is to use a nested Repeater to display the RadioButtons.
The other is to create the controls during the original repeaters. Repeater.ItemDataBound event.
In either case, you need to be very aware of the Page Lifecycle.
You'll want to avoid databinding in the Page_Load event, unless the databinding is being done with an if(!Page.IsPostback) block. If you fail to check for postback, you'll run into issues where the Page_Load calls a DataBind() call that then wipes the values of the repeater before any event handlers can use it.
Alternatively, you can do your binding in Page_Init, which occurs BEFORE the viewstate can be applied, so you won't lose your values.
You can also use USer Controls for the RadioButtons. There's a previous post that covers how to use nexsted user controls within a Repeater here.
Related
I've got a Repeater control, bound to a PagedDataSource, which datasource is a list of custom controls I've made. These custom controls contains a couple of text boxes.
I have a save button, and when it is clicked I want to save the data in all the custom controls to a database, no matter which page they are on - but currently I only got access to the custom controls displayed on the current page.
What I've tried to do is to, in the btnSave_Click event, create a new temporary datasource equal to the current one, except its not a PagedDataSource. That way my repeater contains all custom controls - BUT - the changes made in the textbox fields are no longer available. I then tried to add JavaScript onchange events on the textboxes in the custom control, so that a postback would be fired whenever text was changed, and the property in the user control codebehind would be updated. This didnt work either.
Any ideas?
save the changed values on each page index changing event (or prev /next buttons) into your persistance object (List)
http://www.dotnetfunda.com/articles/show/1611/how-to-select-multiple-records-from-multiple-pages-of-the-gridview-and
The reason your non-PagedDataSource is empty is because the changes in your text box exist in the client and not on the server - you'll need to synchronise the values from your controls with the empty slots in your repeater.
The Repeater does not have built-in Pagination (like the GridView or other complex controls) so it does not offer events such as the PageIndexChanging event. I assume therefore, that you have your own Page navigation implementation. You should therefore call the function you have presented within that implemented function.
Try Using a generic List and Skip and Take methods of that
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 noticed that some controls (e.g. TextBox) keep their changes between postbacks even if the change is made by a client-side script while some others don't (e.g. ListBox). Can anyone explain me why? Is there any way to extend the first behavior to other controls?
Thank you!
It depends on when the ListBox is being data-bound or ListItem are being populated.
Generally, such case would happen when the ListBox is created inside another parent control such as a Repeater, and the Repeater is data-bound at the Page_Load event. Which mean the ListBox actually does not exist until the Page_Load event is over.
ViewState is restored to the ListBox somewhere in between the Page_Init and Page_Load event of the Page Control. If the contents of the ListBox are created during Load event that means the ViewState of the ListBox is not able to restore the contents after PostBack and unable to keep track of and automatically select the new SelectedValue from the PostBack.
If the Repeater in this case is data-bound at the Page_Init event, the ListBox's contents would be ready after the Page_Init event and ViewState is able to restore correctly and automatically select the SelectedValue.
I usually data-bind everything at the Page_Init event to make sure controls are able to work with ViewState correctly.
Have a look at the page life cycle of ASP.NET web form for more details.
http://msdn.microsoft.com/en-us/library/ms178472.aspx
All controls keeps their changes between postbacks - Except if you create them again programmatically.
Probably your ListBox lose the changes because you populate it on every PostBack.
Try to do
if(!IsPostBack)
{
PopulateMyListBox()
}
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 ran into a problem recently when using a repeater that I was adding dynamic controls into and although I've got a workaround that does functionally exactly what I want it to do, I'd like to know if there is a better way to do it for my understanding. I've been working with ASP.NET for about 6 months now, and everytime I think I've got the page lifecycle/viewstate completely sussed something crops up that I can't answer.
I was creating a form where users could register their interest for an event, and register for multiple people.
The aspx went something like:
<asp:Repeater ...>
<bunch of formatting and always there controls like firstname/lastname/address>
<asp:PlaceHolder ...>
<dynamic controls for workshop selection go here>
</asp:PlaceHolder>
</asp:Repeater>
An event can have workshops that the user can register for, and the availability of the workshops is dependant on the date that they choose to go to the event on. The availability of the workshops is dependent on the date, so they can't choose the workshops until they've selected a date.
Anyway the dynamic controls that I'm adding are basically a bunch of literals and a bunch of radio button groups.
I started off by adding the controls in the ItemDataBound event handler, but when saving my repeater items back to my delegate list the ViewState of the radio buttons was never updated. All the fields that were referenced in the ItemTemplate were handled fine, but not the radio buttons I was adding dynamically.
I tried to use the ItemCreated event instead, adding my buttons there, but that didn't seem to make any difference. In the end I settled on a workaround which was based off of this. Basically I'm just outputing the HTML input fields in a literal and reading them back from the request.
It all works perfectly now, and I'm happy with the functionality, it just seems really dirty to have to output the radio buttons as HTML inputs directly rather than use a server side control. Does anyone have a clue about why the ViewState wasn't being restored properly?
Just to be clear, the controls were recreated in the same order everytime, with the ID properly set. I'm using dynamic controls all over the place and they're working fine, I just can't get them to work in this case when I'm adding them inside a repeater.
//more clarification
I can't create these controls in Page.Init as the user selects the date which causes a postback and I have to wait for the viewstate of that control to load before I create the dynamic controls.
You're creating (or re-creating) the controls when the repeater is bound to its data source. If this happens after the ViewState has been loaded by the page, the ViewState won't be available to the dynamically-created controls.
Check you're binding your repeater early enough - Page.Init is OK; Page.Load is too late.
It is worth noting that Radiobuttons controls do not work 'out of the box' in repeater controls. Repeater controls inherit the INamingContainer interface which ensures all rendered html controls have unique name attributes. As radio buttons use the name attribute to group themselves this means you will not be able to create groups of radio buttons i.e. setting the GroupName property will not have the desired effect as the Repeater will override this and create unique names for each RadioButton.