I have a page (page1) with a LinkButton that, when clicked, will take the browser to a new page (page2).
When I click the LinkButton page1 posts back and hits the Init and Load event handlers for page1, and then moves on to page2.
How can I tell in the page1 postback that I am about to be taken to a new page, as opposed to clicking a Button that causes the page posts back but does not navigate away?
You can also add OnClick events to your code behind for each button, and in the case of the one that is to postback to another page, do a Response.Redirect. The limitation of that however is that if you need form data on "page2", you will lose posted form data on a Response.Redirect.
It appears that you're not using the OnCLick event of the LinkButton, If you use the event, perform the action of the click there, not on the Page Load event?
Related
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.
in my project I have two pages, page1 and page2. In page1 I have few dropdown controls to filter the records from the db. And in the grid view I have the button as "View details". When I click the "view details button, the page has to redirect to page2 and complete details of that record will be viewed.
Now what I need is I have back button in page2. when I click that button, the page has to go back to page1 and page should display like how I left it, should not load as fresh page....
Since beginner to asp.net I couldn't find the solution for this issue.
Please provide with some example....
Very thanks in advance...
Try this in you viewdetails button click event:
Server.Transfer("Page2.aspx")
And similarly in your page2 back button click event
Server.Transfer("Page1.aspx")
The Server.Transfer method also has a second parameter—"preserveForm". If you set this to True, using a statement such as Server.Transfer("Page2.aspx", True), the existing query string and any form variables will still be available to the page you are transferring to.
A simple solution would be to keep any such filters that you have set in session.
This allows you to keep the filters active even when the user navigates away from the page.
You can have a button the Page1 to clear the filters.
Page1 Load:
if(!String.IsNullOrEmpty(Session["Filter1"]))
{
dropDownList1.Text = Session["Filter1"];
}
Page1 dropDownList1_SelectedIndexChanged
Session["Filter1"] = dropDownList1.Text;
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.
The situation:
I have user controls with buttons that have hooked events. Controls with events need to be initialized in Page_Load or earlier.
I wish to spawn these user controls dynamically by clicking an Add button.
It is important to remember that events, such as click events, are not fired until just before Page_LoadComplete.
Broken Solution A:
Page_Load: Dynamically create an Add button, hook click event.
User clicks on the Add button, triggers postback.
Page_Load: Creates the Add button as usual, and hooks click event.
Page_Load: Doesn't know that the Add button has been clicked yet, so it doesn't know to spawn the user control!
AddButton_Click: Page finally aware that a new user control should be added upon the next Page_Load.
User cannot see the control they added, because another Page_Load has been triggered.
User reloads the page by clicking a button, refreshing the page, etc.
Page_Load: Creates Add button, and hooks click event. Now aware of added user control, creates user control. Hooks events within the user control.
User clicks on button within user control, triggers just fine.
Result: User has clicked to Add a new user control, the server is aware that the control should exist, but the user does not see it until they trigger the page to load again (by clicking another button, or refreshing, etc).
Naturally, I took a look at the life-cycle, and see that Page_LoadComplete occurs after events, so if I place any event-dependent code in Page_LoadComplete, all should be well?
Broken Solution B:
Page_LoadComplete: Dynamically create an Add button, hook click event.
User clicks on the Add button, triggers postback.
Page_LoadComplete: Creates the Add button as usual, and hooks click event.
AddButton_Click: Page aware that a new user control should be added upon the next Page_LoadComplete.
Page_LoadComplete: Aware of the button click, dynamically adds the control, with its own internal button click event.
User clicks on button within the added user control, but it does not trigger!!
Result: Everything works great, except the button within the added user control is inert.
The conundrum is: I need controls to spawned by a button click, which means I need to put my Controls.Add(...) code in Page_LoadComplete. Inversely, I need the controls being added to have working events, which means the Controls.Add(...) code need to be in Page_Load. I have a perfect dichotomy.
The only janky solution I can think of is taking solution A and forcing the page to reload manually after clicking the Add button, which is a waste of bandwidth and processing.
This might not be the best practice, but you can check Request.Form for the evidence of add button click during the Page_Init event and add the controls there. It should solve your problem.
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