I'm using ASP.NET 4 to create a page with elements that are used in a jQuery UI Sortable plugin.
All of these elements contain a button (implemented as a submit button) with the name SubmitButton. All but one of these buttons are hidden in the page's Load event. But if I drag the element to another position, and then submit the page using that button, ASP.NET gets confused.
ASP.NET thinks I've clicked a different button, one that wasn't even visible on the page, but is associated with content at the position where the clicked button was before the move. (If I don't move the element, it works fine.)
I can't seem to determine how this is happening. As I understand it, ASP.NET knows which submit button caused a postback because the button's name and value is included in the postback data. (__EVENTTARGET plays no role here and is empty.) So how can it think a different button submitted the page?
How could ASP.NET get confused about which button submitted the page?
(Sorry, it's not possible to put this page on a public website.)
I worked through this issue and here's what I found.
First of all, buttons by default are rendered as <input> tags with type = submit. The postback mechanism in this case has nothing to do with ASP.NET. The postback data includes, among other things, the name of the submit button that caused the postback along with the button's text (in the form name=text).
But ASP.NET button names, by default, include the names of all parent controls. When those controls are unnamed, they are given an ID like ctl00, ctl01, ctl02, etc. The result is that all my buttons are guaranteed to have a unique name.
The problem is when these buttons and parent controls are all created dynamically. On the postback, these controls are reconstructed in the load event but in the new order. Because the order affects the name (ctl01 vs ctl02), this means my submit button has a different name than it did when the page was originally rendered.
The result is that ASP.NET sees the wrong name associated with the submit button used to trigger the postback.
Related
I have the following scenario:
UserControlA contains a <asp:Button id="bSomeid" onClick="AddItem" /> with some code to an item to a shopping basket in AddItem.
UserControlB contains some LinkButton's that dynamically add a selection of UserControlA to the page in the OnClick event.
This is all done in an UpdatePanel. It is a little more complicated but I have pruned the information to what I believe is causing the problem, I will add more information if necessary.
The problem I have is that it takes 2 clicks for the AddItem event to trigger after I have added the items to the page after clicking the LinkButton.
I understand why this is happening - it is to late in the page cycle to register events for the next post back in the onclick - but can anyone think of a way around this? Can I force an event to be triggered on the next postback? I have tried to think of a way to run my code in page_load but I requuire access to the sender in the onClick.
Using .NET 4.0.
EDIT
I managed to find a way to get the link button sending the request in the Page_Load (using Request.Form["__EVENTTARGET"];) so I moved my code to the Page_load event. It still requires 2 clicks so I am assuming it isn't something to do with the onClick being registered to late.
Are there any other general things to check that could cause a button to require 2 clicks to post an event properly?
If your suspicion about being late in page life cycle is true then you can try using ScriptManager.RegisterAsyncPostBackControl method to register dynamically added controls in the link button click - considering that your button is within user control, you need to add public method into UserControlA that would actually register the button bSomeid1 and link button click from UserControlB would actually call the A control's method.
EDIT :
Another cause for button click not happening can be that button being dynamic control is not added in the page hierarchy when post-back happens (or it gets added very late in the page life cycle when the post back data is already processed). A really full-proof solution should add dynamic controls back to the page hierarchy in page_load it-self (and strictly maintaining same controls ids within hierarchy). If that's not possible then you can sniff the request (Request.Form) to detect the post-back.
In your case, you should ascertain if the button is indeed causing the post-back on each click. If yes, what is the POST data (Request.Form) for the first request - what is the __EVENTTARGET value on the first click (and post-back)? That should start your trouble-shooting.
On the other hand, a simple work-around could be to use html anchor element (you can still use link button) and have a javascript handler in the click event that would set some hidden variable and then submit the form (you can simulate the click on hidden button to trigger ASP.NET client side submit pipeline) . Now the hidden variable value can be used on the post-back to determine which link button has been clicked.
"Are there any other general things to check that could cause a button to require 2 clicks to post an event properly?"
Does it require two clicks on the control, or does it take accept a single click elsewhere on the screen, and then fire first time with a single click on the control?
I have my own (similar) issue with the Updatepanel where the first (expected) trigger does not fire and it seems that a single click elsewhere, and then the subsequent triggers fires first time (which totals 2 clicks)
[edit] Since you are working on this ATM, it may help me as well. Do you have a textbox with a trigger event on it? I do, and if I leave this blank (so that it does not fire) then there is no need for a second click.
In an ASP.NET 2.0 project, I've got a form that's used to edit a rather complicated data type. The form is largely contained in an UpdatePanel, because sections of the form appear and disappear based on selections in dropdowns and radio buttons. The Save and Cancel buttons are not in the UpdatePanel.
I've designed it so that on Page_Load I deserialize the object I'm editing from ViewState and update its properties from the controls on the page. Then in OnPreRender I update the controls with new visibility/values based on the object's properties, and serialize the object back into ViewState.
I'm having a problem where I can consistently get this error briefly:
Sys.WebForms.PageRequestManagerServerErrorException: An unknown error
occurred while processing the request on the server. The status code
returned from the server was: 0
There is a panel on the page that appears/disappears based on a selection in a dropdown above it. The dropdown has AutoPostBack set to True, but it has no event handler attached; it causes a postback, which means the object is edited in Page_Load, and the panel's visibility is updated in OnPreRender based on the object's new state. Also, the dropdown is the default focused control when the page loads.
The repro steps are as follows:
Open an object for editing
Without clicking anything, press a key on the keyboard to change the dropdown's value.
Changing the dropdown with the mouse causes a partial postback and updates the panel's visibility. Changing with the keyboard doesn't do anything until focus leaves the dropdown.
Click the Save button. The error appears briefly, then the page refreshes and the object is saved successfully.
As noted, the dropdown doesn't post back until it loses focus after being changed with the keyboard. I think what's happening is that clicking the save button changes focus from the dropdown and starts the postback from the dropdown at the same time as the postback from the Save button. This is why the error comes up.
So what is the best solution? I could make that control not be the default focus, but it's still possible to make the error happen through creative use of the tab key. Is my overall design here unwise?
UPDATE: This question seems to be the same issue; their solution is to simply hide the error message. Is this wise?
I am unfortunately having to work with asp.net web forms. I have a label that has a different Text property every time the page loads. I have a button that is clicked. I have double clicked on the button and it has shown me a code view.
I get a reference to the label via labelID.Text, but it refers to the value of the text that is about to be displayed on the next page load. How would I get the text of the value when the button was actually clicked? Or is web forms not advanced enough for that.
Search where the labelID.Text is modified (maybe Page_Load event), and save the text before in a global variable.
It sounds like on every page load or postback, somewhere there is code which applies a new value to labelID.Text. Where is that work being done? Page_Load?
In any case, wherever that work is being done, you most likely have access to both the existing text value of the control, and the new text value you're about to give it.
I have a user control I am adding dynamically.
It has a link button and a text area on it. The containing div is hidden via style sheet (client side), and I use some jquery to pop it up in a modal.
It is getting added in the init and the button click event is firing on the server.
BUT the textareas value is not being set. On further inspection the field value is not even being sent in the form POST data.
Any ideas why the value is not being sent. The rest of the form values are being sent with no problems.
Make sure the control is actually being added to a form control. Your link button will still post back even if it's outside the form as it's a javascript call, but there won't be any content from your server controls in postdata.
I have a ListView on a page that displays a list of widgets. When a user clicks on one of the items in the list, I want to display a ModalPopup that contains controls allowing the user to operate on the item they selected.
I could easily accomplish this by placing a Panel and a ModalPopupExtender in the ListView's ItemTemplate, but this mean one set of hidden controls for each and every widget, which would massively bloat the page size. (There are going to be some rather heavyweight controls in there.) Instead I want to reuse a single ModalPopup for each of the widgets in the list.
I've done some searching but I haven't found anything that applies directly to my situation before. From what I've been able to figure out, however, I have to do something like this:
Place a Panel and a ModalPopupExtender on the page inside an UpdatePanel.
Build a custom WidgetManipulator user control that has a WidgetID property. Put this in the Panel, along with a couple OK/Cancel buttons.
In Javascript on the page, attach a click handler to each widget in the ListView that triggers a postback on the UpdatePanel.
On the UpdatePanel_Load event on the server, display the ModalPopup and then set the WidgetID propety on the WidgetManipulator to the ID of the clicked widget.
On the OKButton_Click event or CancelButton_Click event on the server, hide the ModalPopup. If OKButton was clicked, call WidgetManipulator.SaveChanges() first.
The part I haven't figured out is: How the heck do I know what widget was clicked on, and how do I pass that back to the server when I refresh the UpdatePanel? Is this even the right approach at all?
If you can use jQuery instead you could do something along the lines of these two posts:
Modal Delete Confirmation Version
Two Using jQuery SimpleModal Plugin
Demo
Inserting Content Using
jQuery SimpleModal Plugin Demo
When I need to pass data from client to server in ASP.NET AJAX, I generally use an asp:HiddenField with runat="server". Both can see it freely, but beware potential postback asynchronicity.
Sounds like you need to notify the server the widget was clicked - You may use a Timer to postback; or I'd go with option 5.