Not sure if this is the prescribed order of events, but I have a logout button on my masterpage, whose event doesn't fire until after the content page's page_load fires.
On some pages there is some time-consuming code in page_load, and this makes the logout process take way too long.
The catch-22 is that in the content's Page_Load, I can't check any property I might set in the Master's logout_click event, because it hasn't fired yet.
How can I make the MasterPage's logout button fire first and go directly to the redirect which I have in the click event?
Thanks very much,
JimO.
What you are facing is the default behavior due to page life cycle.
But you can try the following steps to work around your problem
Instead of having a Button/LinkButton and writing code for LogOut on master page in Click event, you can have a HyperLink.
Set its NavigationURL to point to a logout page which will handle only the code for LogOut.
Write the LogOut code in the Page_Load event of that page.
Most people put something like the following in their page_load
if (!Page.IsPostBack()) {
// do stuff to initialize everything
}
This way when a postback occurs you don't necessarily have to reload a bunch of stuff.
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.
I'm using ASP.NET 4.0 with a LoginStatus control in a Master page. When the status is Login and I click the link, the current page is attempted to be reloaded. I can see that IsPostBack=True.
If I use Set Next Statement to avoid my code in Page.Load the redirect to Login.aspx goes without a hitch, otherwise the current page tries to reload and for some reason it fails.
From Page.Load, what is the best way to detect that LoginStatus has been clicked? A click event handler won't work since it fires too late. IsPostBack won't work either (on its own). I do have a BaseMasterPage class that is inherited by my Master page, but again, the Master page loads after Page.Load in all of my pages.
Do I have to handle this click in every one of the pages that use this Master page?
Btw, I also have a BasePage class that all of my pages inherit. I'm just not sure how to detect that LoginStatus has been clicked - and if it has, how to handle it. Would I force a Redirect? That seems like overkill...
The problem here was being caused by an <img src= that did not exist on a remote server. This was causing my page to load twice. The first time through, IsPostBack would be True. The second time through it was False.
This is why I was unable to figure out why the redirect wasn't happening on its own. I'm marking this question as answered even though I should probably just delete the whole question. :S
I am having an issue with an image button being clicked, and then the on click event of that button is not being fired, part of the issue I think is that a validator on the page is firing and then suppressing the button click, but I cannot find what is causing it.
Is there any way to see the events that a request goes through?
I assume that there is something is happening before the post back occurs, as I can catch the page as it comes back to Page_Load, but I need to know what is happening before that.
Is this even possible to find out?
is it an ImageButton ? If yes, set CauseValidation to false.
You can get some info by enabling tracing for the page.
Before Load, you only have PreInit at the Page level, followed by Init for all Controls (bottom-up), Init for the Page, then InitComplete for the Page, then Load for the Page, then Load for all Controls (top-down).
I have two radio button on my asp.net page, with AutoPostBack = True
When I click on either of those, they each set a flag SaveData=False
However, when I click on them, the page_load event occurs first, so the page_load event saves the data, then the radiobutton_OnCheckedChanged event is triggered.
How can I trigger the OnCheckedChanged before the page_load event?
You can't.
You need to read up on the page lifecycle.
You can't trigger the OnCheckedChanged before radiobutton_OnCheckedChanged because that's the normal page life cycle.
You can check in Page_Load if Page.IsPostBack is true or not, and then don't save (or save) the data.
Troy - you will have to take care of this on the client side (javascript / jquery).
Your AutoPostBack = True causes the form to do a postback which calls page load.
Its all about how the page lifecycle and server side events work.
You can't the page always needs to load before events can be fired. This has to do with control creation, view state management, control state, etc.
What you want to do in your Page_Load is something like:
if(!this.IsPostBack)
{
// Do the stuff you want on the initial page load
}
Anything that you do not want to happen when the radio buttons are clicked, put it inside the if {} block. IsPostBack indicates that the page is processing a post-back event, which is what happens when you click one of your radio buttons.
You can't change the order/sequence of event handler execution. However you may move the code inside the page_load to another event handler.
When loading a page for the first time (!IsPostback), I am creating a button in code and adding it to my page, then adding an event handler to the click event.
However, when clicking the button, after the page reloads, my event handler does not fire.
Can anyone explain why?
#Brad: Your answer isn't complete; he's most likely doing it too late in the page lifecycle, during the Page_Load event.
Okay, here's what you're missing.
ASP.NET is stateless. That means, after your page is rendered and sent to the browser, the page object and everything on it is destroyed. There is no link that remains on the server between that page and what is on the user's browser.
When the user clicks a button, that event is sent back to the server, along with other information, like the hidden viewstate field.
On the server side, ASP.NET determines what page handles the request, and rebuilds the page from scratch. New instances of server controls are created and linked together according to the .aspx page. Once it is reassembled, the postback data is evaluated. The viewstate is used to populate controls, and events are fired.
This all happens in a specific order, called the Page Lifecycle. In order to do more complex things in ASP.NET, such as creating dynamic controls and adding them to the web page at runtime, you MUST understand the page lifecycle.
With your issue, you must create that button every single time that page loads. In addition, you must create that button BEFORE events are fired on the page. Control events fire between Page_Load and Page_LoadComplete.
You want your controls loaded before ViewState information is parsed and added to controls, and before control events fire, so you need to handle the PreInit event and add your button at that point. Again, you must do this EVERY TIME the page is loaded.
One last note; page event handling is a bit odd in ASP.NET because the events are autowired up. Note the Load event handler is called Page_Load...
You need to add the button always not just for non-postbacks.
If you are not reattaching the event handler on every postback, then the event will not exist for the button. You need top make sure the event handler is attached every time the page is refreshed. So, here is the order of events for your page:
Page is created with button and event handler is attached
Button is clicked, causing a postback
On postback, the page_load event skips the attaching of the event handler becaue of your !IsPostback statement
At this point, there is no event handler for the button, so clicking it will not fire your event
That is because the event binding that happens needs to be translated in to HTML. This postback that happens if bound to the page between OnInit and OnLoad. So if you want the button to bind events correclty make sure you do the work in OnInit.
See the Page Life Cycle explaination.
http://msdn.microsoft.com/en-us/library/ms178472.aspx