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How do you call OnPageIndexChanging from Javascript?

I have code that when a user wants to page through a GridView, it asks them (using a JavaScript confirm) if they want to save the data from the grid.
So, I'm able to get the confirm to work (with the code-behind saving function), but I'm noticing that it's not firing the OnPageIndexChanging method - which basically defeats the purpose here.
So, to summarize, can JavaScript access the OnPageIndexChanging method?
Thanks a lot

The OnPageIndexChanging event is a server-side event, so it's not surprising that your Javascript handler isn't getting triggered.
I'm not sure if ASP.Net has a "built in" way to do this; but you can do it by attaching your own Javascript listeners. Here is the general approach (I'm using JQuery to make it easier):
Write a JQuery selector that gets all the paging links that you want to confirm.
Add a click listener for each of those links
Make the confirm function the handler for those listeners
So, the code would look something like this:
$("#grid a").each(function () {
$(this).click(function () {
return confirm("really?");
});
});
Notes
Here grid is the ID of the GridView control, so #grid a selects every a tag within my grid.
Using return confirm() returns false if the user does not confirm, which effectively cancels the click event.

How do I cause a Postback?

I need to cause a postback in c#, how can i do this? (It can not be through a button or any other element) Just want to cause a postback if a condition is met.
something like
If(so and so)
Postback now!
else
Do not post back

From the comments it looks like you are using telerik's RadTabs. You could potentially set AutoPostBack to true on the tab control so that it would force a refresh whenever the user switches tabs.
http://www.telerik.com/help/aspnet/tabstrip/tab_server-side%20events.html

Your question does not make sense.
C# code runs on the server, in response to a postback.
Until a postback happens, no code can run.
You may want to trigger a postback in Javascript, which runs in the browser.

Some didactic contextualization: whatever piece of code you are trying to call in your "second postback", just call it in your "first postback" already!
Example:
You have a method you want to call, say, a Button_Click in your "second postback"? Just call it in you "first postback":
btnSaveClick(btnSave, null);

You can always do a Response.Redirect(Request.RawUrl);.
You'll want to be careful that you don't cause an endless redirect loop.

To force a postback in Server code, use ClientScript.GetPostBackEventReference() to generate the javascript code that does the postback. Then add a startup script in your event handler that calls the postback javascript.
aspx:
// Do an empty postback that doesn't do anything.
function doPostback() {
<%= ClientScript.GetPostBackEventReference(btnDoPostback, String.Empty) %>;
}
<asp:Button ID="btnDoPostback" runat="server" OnClick="btnDoPostback_Click" Style="display: none;" />
cs:
if (!IsPostBack) {
ScriptManager.RegisterStartupScript(this, this.GetType(), "dopostback", "doPostback();", true);
}
protected void btnDoPostback_Click(object sender, EventArgs e)
{
}

You can't do a postback in your code-behind. Your code-behind code IS your postback code. Why are you trying to do this? Maybe we can help you in your program logic

Did you want to call the page again? You can do this with a Response.Redirect

Do you mean on your .aspx/cshtml pages? If so use jquery's $.post
If you really are in a controller (and you are already running in response to a postback) then you should probably refactor your code so that whatever logic you want to call (via your 'second post' back) can be called from your existing location as well as your other Post action.

call jQuery function from code behind after postback

I'm trying to call a jQuery .click function after page postback from code behind. I'm using ASP.NET with C#.

The easiest thing to do would be to use jQuery to attach to the submit event of the form and do whatever processing you require before the postback.
$('#form-id').submit(function() {
// Do whatever here
});
Also, if you return true from this event handler the postback will occur, if you return false then the page postback will be prevented.

If you want to call the click function for an element after the page has successfully reloaded from a postback, you can make use of the RegisterStartupScript function:
Page.ClientScript.RegisterStartupScript(Page.GetType(), "PostbackClick", "$('#myElement').click();", true);

how can i call a javascript function when an ASP.net validation summary is filled

i have a validationSummary in my page. i want to call a javascript function after the validationSummary is filled. how can i achieve this?
i think i should add an attribute in the code behind, but i can't figure out what is the attribute's key.
any help?

You will want to call the javascript function Page_ClientValidate() to initiate the ASP.NET validation wired to your page controls. Once this is called, the Page_IsValid boolean value will be properly set.
Here is an example of how I am using it. If ASP.NET validation is successful, I disable the button, otherwise the button remains enabled and the validation summary is displayed to the user. The OnClientClick is from a ASP:Button control.
OnClientClick="javascript:Page_ClientValidate(); if (Page_IsValid==true) { this.disabled=true; }"

I don't think that's possible. It is, however, possible to intercept validation by setting OnClientClick on the controls that do postbacks. Then you can check the global JavaScript variable Page_IsValid for the validation result.
One thing to keep in mind is that, when there are no validators on a page, Page_IsValid will be undefined.

I started to implement the solution by #EverettEvola but also where the validation logic was being called multiple times and displaying multiple ValidationSummary popups. My solution was as follows:
On the button (in my case the button was a submit button)
OnClientClick="return CustomValidationOnClick()"
And the CustomValidationOnClick()
function CustomValidationOnClick(source, args) {
//Manually kickoff page validation
//This call will display the Validation summary popup if page is invalid
Page_ClientValidate();
//Page_IsValid set by the result of the Page_ClientValidate() call
if (Page_IsValid == true) {
this.disabled=true;
return true; //if Submit button return true to continue form submit
}
else {
//do whatever here
return false; //if Submit button return false to cancel form submit
}
}

Client-Side validation prvent Manually Postback by JavaScript eval()

I encouter some postback issue when using GetPostBackEventReference. Here is the Scenario:
I have a javascript modal popup dialog and got a button in this modal dialog which used to select things (this is NOT an asp:button control)
When this javascript dialog HTML button is clicked, it will call the MS AJAX web service call by the javascript: eval() method. And this MS AJAX web service call is dynamically generated. So the code is like this:
var serviceCall = svcCall + "(" + parameters + ")"; //dynamically generate the MS AJAX web service call here
eval(serviceCall);
//use eval to trigger the MS AJAX web service call
As you may all know, after complete the MS AJAX web service, you can define a callback function to handle the completion:
function OnComplete(result, userContext, methodName) {
//force to call postback manually
eval($(userContext[0]).val());
//close the javascript dialog here
}
As I have mentioned before, the MS AJAX web service call is built dynamically, and when the MS AJAX web service call is construct, it will be passing a userContext which contain the postback value (i.e. "__doPostBack('ctl00$ContentPlaceHolder1$btnSelectUser','')", so when the javascript eval() is called, it simulate a asp:button click postback.
The userContext[0] basically holding a asp:hidden field's ClientID, and the hidden field's value is set during the Page_Load event:
protected void Page_Load(object sender, EventArgs e)
{
btnSelectUser.ValidationGroup = "popupSelect";
btnSelectUser.CausesValidation = false;
this.hdnBtnPostback.Value = Page.ClientScript.GetPostBackEventReference(btnSelectUser, string.Empty, false);
}
As you can see, this is how I bound the asp:button (i.e. btnSelectUser) 's Click Event to the asp:hiddenfield using the GetPostBackEventReference, and set the registerForEventValidation argument to false. I have also tried to use different ValidationGroup and set the CausesValidation to false, but no hope. :(
In summarize, I bound the asp:button's Click PostBackEventReference(i.e. __doPostback(....)) to the asp:hidden field's Value attribute, and using javascript eval() to eval this hidden field's value in order to manually trigger postback.
p.s. the btnSelectUser is an asp:button control and used to call out the javascript modal dialog.
Ok, here is the Problem:
In the same page, there is some asp:validator, e.g. and , and of coz, when the page run into error, this validator and callout will display to the user. e.g. When the user didn't fill in anything and submit the form, the ValidatorCalloutExtender will display a ballon and tell the user. Imagine one of this ballon/validatorCalloutExtender come out and on top of your screen at the moment.
Then you click the btnSelectUser (asp:button) to show the javascript modal dialog, and in the dialog, you Add some users, and once you hit the SELECT button inside this modal dialog, a MS AJAX web service is trigger as mentioned above, and once this web service is complete, it eval() the asp:hidden field's value (i.e. __doPostback(...))......and do the postback manually.
However, because of the validatorCalloutExtender ballon has display, it somehow cannot trigger the postback in this way, but when I close the ballon/validatorCalloutExtender, the manual postback using eval() is just working fine. Even more strange is that, when the ballon is displayed, the first time I click the SELECT button inside this modal dialog it doesn't fire the postback, however, if I do the same thing again (i.e. open up the javascript dialog, and choose some users, then click the SELECT button again). It able to do the manual postback....and I don't understand why the first time doesn't work.
This has really drive me crazy, hope anyone here can help, would be really appreciate. Thank you so much folks. :)
Have a nice day. Looking to heard from you all shortly.

When you call __doPostBack(eventTarget, eventArgument) a form submission is triggered:
This from post will proceed if WebForm_OnSubmit(); return true.
WebForm_OnSubmit result depends on ValidatorOnSubmit result, which in turn depends on
ValidatorCommonOnSubmit result if Page_ValidationActive == true.
Now if you are still with me, as in the function below:
function ValidatorCommonOnSubmit() {
Page_InvalidControlToBeFocused = null;
var result = !Page_BlockSubmit;
if ((typeof(window.event) != "undefined") && (window.event != null)) {
window.event.returnValue = result;
}
Page_BlockSubmit = false;
return result;
}
The result of ValidatorCommonOnSubmit depends on Page_BlockSubmit, so the only thing to block your postback is Page_BlockSubmit == true, it has nothing to do with validation callouts.
I was unable to simulate your case, but if you could post a full code sample it will help me track down the issue.