Going For AJAX: postback

Showing posts with label postback. Show all posts

Wednesday, March 28, 2012

How do I update text in a panel using ajax and a timer?

This is a pretty basic question, I just need to update a textbox every few minutes without using a postback. The text is pulled from a sql query. Is there a example for how to do this somewhere? (simialar to how gmail updates, etc...)

Take a look at this: http://encosia.com/index.php/2007/07/25/display-data-updates-in-real-time-with-ajax/

If you're only updating a simple text label, you could skip the UpdatePanel in my example andupdate that text on the client side, using a web method.

A combination of those two examples should give you what you're after.

Thanks for providing links.

How do I show postback search results on a Modal Popup?

My goal is to show the serach results in a grid view on a model popup after the user enters the search criteria on a page and presses the search button. The OnClick event handler needs to collect the search criteria, get the dataset after querying the database and bind the data to the gridview before displaying the modal popup.

My problem is that the search button's id can't be assigned to the TargetControlID of the ModalPopupProperties as it will not let the OnClick event be fired and process the postback.

Please suggest the solution/workaround.

Thanks much

Display the ModalPopup via script instead?

David,

Do you have an example or a sample of the script that I can take a look at?

The other option would be to dynamically create the popup, after I process my search funcationility. But the question is, how do I invoke the display of the popup after associating the TargetID of the search button to the dynamically created ModelPopup?

Thanks for looking into it.

Vijay

I believe the following post outlines how to display the ModalPopup with script:http://forums.asp.net/thread/1280980.aspx

How Do I Reset Scroll Position Inside UpdatePanel?

Hello,

I have a UserControl inside an UpdatePanel. The UserControl contains several DIVs that I show and hide through partial postback. I want the contents of each DIV to be scrolled to the top when I show it. I have tried using the ScriptManager to set focus onto the topmost control of each DIV when I show it, but it doesn't work. I have also tried through javascript to no avail. I know this is kind of the opposite of the behavior that many folks want from AJAX, but I need it for this piece of my application. I have tried searching but all examples are page-centric, not usercontrol-centric and speak to SmartNavigation.

Any help is appreciated.

Brendan

not sure if this would help, but I found something interestingin terms of firing off some js code during a partial page update :

http://ajax.asp.net/docs/ClientReference/Sys.WebForms/PageRequestManagerClass/default.aspx

It was particularly useful for displaying a message to the user to indicate something was happening...

Good luck,

Bob

I ended up just using this in the codebehind of the ascx:

ScriptManager.RegisterStartupScript(Page,typeof(PageTemplate),"Focus","focus();",true);

And including this function in a .js file (one line for each section):

Seems to work on all but the initial page change, which is 'good enough' for me at this stage.

Monday, March 26, 2012

How do I get Javascript Inside Content Template to fire on postback

I have 3 ASP controls inside of a ContentTemplate (some of mysyntax may be a little off below (doing it from memory here) but you'll get the idea):

<asp:dropdownlist id= "control1" runat="server".../>
<asp:dropdownlist id "control2" runat="server".../.../>
<input type='button' onclick ='changeControlVisibility();' "control1".../>
<script type='Javascript>
'changeControlVisibility();
</script>

</contenttemplate>

Now, the''changeControlVisibility' javascript SETS a hidden value back and forth from 1 to 0 each time its clicked,AND it sets the 'style.visibility' property of both Control1 and Control2 .

So, when the changeControlVisibility runs during the the Load of the page, Control1 is then visible and Control2 is not visible. After the page has been loaded, each time the BUTTON is clicked after that, its the opposite actions (control1 =hidden & control2=visible) to (control1-visible & control2=hidden). This all works great.

The issue is this, when the selectedindexchanged of either of the dropdowns fires a postback (which is what I want) the

<script type='Javascript>

'changeControlVisibility();

</script>

never gets called or run, therefore all the controls within the contenttemplate get set to style.visiblity =visible (so they all appear) becasue that script never gets called during the postback.

Any suggestions on how to get it run or any good workarounds?

Thanks very much and I will immediated mark the issue resolved to the genius who comes up with a solid answer.

You can solve this by having that JavaScript outside of your UpdatePanel (in the <head> tag would work) of your page and then call it everytime the UpdatePanel gets updated. Have a look at the PageRequestManager class which enables you to execute JavaScript before, during, after UpdatePanels are loaded.

scripttype="text/javascript">
Sys.WebForms.PageRequestManager.getInstance().add_pageLoaded(pageLoaded);
function pageLoaded(sender, args){
if (args.get_panelsUpdated().length > 0){
changeControlVisibility();
}
}
</script>

That's a basic example and you can add better checks for specific UpdatePanels but you get the idea.

thanks, that sound like the answer.

last thing, it looks like in your example that the line 'Sys.WebForms.PageRequestManager.getInstance().add_pageLoaded(pageLoaded);'

is adding a new script, if I am wanting to call an existing one, is there a differnt even I should use?

Never mind, i get it now...

So when I create my javascript then

'Sys.WebForms.PageRequestManager.getInstance().add_pageLoaded(pageLoaded);

is actually part of my actual javascript.

thanks so much!

Cool. Yes.

I had started to reply to your other message:

"
pageLoaded is name of the handler method that gets called, you can name it anything and have it execute any existing script also.

Details about the pageLoaded event can be found here:
http://ajax.asp.net/docs/ClientReference/Sys.WebForms/PageRequestManagerClass/PageRequestManagerPageLoadedEvent.aspx
"

Sounds like you've got it.

Cheers,
Al

Thanks Al you made my day!

How do I execute JS on page load after postback within an update panel?

I am trying to scroll the page after it loads between postbacks within an Update Panel. I used to have this work with beta 1

I am not sure how I came up with this, but it doesn't work with Beta 2 any more. Any ideas of how to implement the same functionality?

Thx
dB.

found a solution for this -http://forums.asp.net/thread/1418207.aspx

<scripttype="text/javascript">
function onAutoScrollControlLoad() { window.location.href ='#<% Response.Write(ScrollLocation); %>'; }
Sys.Application.add_load(function() { onAutoScrollControlLoad(); });
</script>

How do I distinguish between AJAX postback and regular postback?

I just installed Ajax 1.0 with VS2005 SP1 and am trying to add AJAX to an existing site.

However, the site right now has fairly complex code in the master page defined in Page_init, Page_load, and PreRender events. I'd really like to skip those calls if it is an AJAX post back. I looked at the Page class and found IsCallBack and IsPostBack, both of which will not be triggered by an AJAX post back.

I thought of using a hidden variable (something like AJAXCall) and using a Javascript to set a value with every control that can trigger an AJAX postback, but that seems like not the right way to do it.

Does anyone know how to tell the difference between the two, or is it possible to skip Page_init, Page_load, and PreRender events with an AJAX call?

Thanks,

Ming

Yes you can, but you have to use UpdatePanel.

Girijesh:

Yes you can, but you have to use UpdatePanel.

I have tried the following setups with no success. In the master page, I included my script manager. Then I had an update panel with a button which updates a label with the system time. This takes about 10 seconds to update. The debugger tells me it executes Page_Load, Page_Init and PreRender.

Then I tried to include an update panel with a button inside page that inherits the master page, it also goes into all 3 methods. I tried this with my existing website, as well as a brand new AJAX enabled website.

Any ideas?

Thanks,

Ming

Hi Ming,
You can use ScriptManager.IsInAsyncPostBack property to distinguish them.
Hope this helps.

Raymond Wen - MSFT:
Hi Ming,
You can use ScriptManager.IsInAsyncPostBack property to distinguish them.
Hope this helps.

It worked like a charm. Thanks for telling me exactly what I was looking for.

Thanks!

How do i clear/reset a cascadingdropdown?

i have three dropdownlists. once i've selected third i fire a postback using the third dropdown's autopostback property. my question is how do i get all the dropdowns to reset back to their prompt messages ready to be used again.

i've tried changing the selectedindexes for the dropdowns to 0 and -1 but that doesn't work

Check outthis thread.

isn't there an easier way of doing this? Seems like a lot of work just to reset the dropdownlists

Hi Iljones,

Based on my research, I think the best solution is to modify the source code to meet your expectation. Here is another sample, please add the code below to your source code. When the last CascadingDropDown populated , onpopulated function will be called and it will set the first CascadingDropDown's selectedIndex to be 0.

Hope this help.

Best Regards,

Jonathan

Jonathan Shen – MSFT:
Hi Iljones,
Based on my research, I think the best solution is to modify the source code to meet your expectation. Here is another sample, please add the code below to your source code. When the last CascadingDropDown populated , onpopulated function will be called and it will set the first CascadingDropDown's selectedIndex to be 0.
<script type="text/javascript" language="javascript">
var flag = true;
function pageLoad(sender, args){
$find("myCDECity").add_populated(onpopulated);
}
function onpopulated(sender,args){
if(flag){
flag = false;
$get("<%=dlState.ClientID%>").selectedIndex = 0;
$find("myCDECity")._onParentChange(false);
$get("<%=dlCity.ClientID%>").disabled = true;
}
}
</script>
Hope this help.
Best Regards,
Jonathan

i'll give this a go today and let you know how it goes. Thanks Jonathan

Probarly to late, but here is an answer anyway.

CS: protected void Reset_Click(object sender, EventArgs e) { CascadingDropDown1.SelectedValue = null; }

Saturday, March 24, 2012

how do I access data on client side with ajax

hello. I have an mdb that I want to use to popluate some textboxes with out postback or waiting for IE to reload.

I am using easylist box that gives me the record ID but I want to use that ID to pull data from the MDB with out reloading the IE.

can someone link me in the right direction?

You should issue XmlHttpRequest on some Javascript event (say, button click or focus removed or whatever), which will pass your ID to the server side and will get the response, which you should dynamically insert into the TextBox you want (javascript, client side again).

This is th schema in general.

You can find a lot of free books about AJAX on the net, ex.: http://paperolli.com/default.aspx?keyword=ajax

thanks!!!

How do a postback on Tab change (ajaxToolkit:TabContainer)

Please help - very simple question.

From documentation onajaxToolkit:TabContainer

TabContainer Properties
ActiveTabChanged (Event) - Fired on the server side when a tab is changed after a postbackOnClientActiveTabChanged - The name of a javascript function to attach to the client-side tabChanged event

When tabs changed, I need to know what tab was changed and populate the related dynamic content.

I have the code (see below) wher OnActiveTabChanged="TabChangedServer" never gets fired and do a postback on Tab change. How can I make it to do a postback!?

<ajaxToolkit:TabContainer runat="server" ID="Tabs" OnClientActiveTabChanged="ActiveTabChanged" OnActiveTabChanged="TabChangedServer" >

Thanks

Nat

I found a solution myself. See my post athttp://forums.asp.net/thread/1554862.aspx

Me too!

http://forums.asp.net/t/1074271.aspx

how can postback use ajax.net beta2

in atlas

var postBack =new Sys.WebForms.PostBackAction();

postBack.set_target("ctl00_MainContentHolder_btnAccAdd");

postBack.set_eventArgument('');

postBack.performAction();

but beta2

Sys.WebForms.PostBackAction object not exist

how can i do it?

hello.

xml-script and actions are defined in the value-added bits. download the november ctp and install it. thena dd the previewscript.js file to your page and everything should work ok.
o~ thank you very much~~ Big Smile

Wednesday, March 21, 2012

How can I tell the difference between an AJAX and a regular postback in the Page_Load even

Is there anyway to determine if the page is called through an AJAX or a regular postback in the Page_Load method, kinda like you can determine if it is a postback or the initial request via the Page.IsPostBack property?

I hoped the Page.IsAsync could be used for this but it doesn't seem to work like I expected.

I think when an AJAX does a post back you cannot access any controls like Label's, buttons etc...so try accessing a label by going label.text, if it fails catch the Exception...not a good way to do it, but a cheaky option for a quick test.

if the button clicked or postback occur, the page.ispostback will be true.

if you are using ajax then the page.ispostback will be false.

this can differentiate those methods.

What you're after is ScriptManager.IsInAsyncPostBack.

Sathesh_pandian:
if the button clicked or postback occur, the page.ispostback will be true.
if you are using ajax then the page.ispostback will be false.

Test that.

You'll find that Page.IsPostBack is actually true during partial postbacks.

That's it. ScriptManager.IsInAsyncPostBack does the trick. Thank you. Big Smile

it will not work when we are using it for different page.

calling another page.

That's because that isn't a postback.

How can I stop the modal popup from disappearing when a postback occurs?

Hello,

I have a problem.
How can I stop the modal popup from disappearing when a postback occurs.

For example, if I have a button on the modal "form", a click makes it dissappear.

Help!