The best explanation I've found for a postBack is from Wiki.
a postback is an HTTP POST to the same page that the form is on.
While the article does explain how a second page was needed in ASP, but no longer needed in ASP.NET, it doesn't give much detail or background. I am looking for a freakin' tome of information on PostBacks. Much like the simple question of "how can I clean a house" can be addressed by this 900 page book. I don't need 900 pages worth, but details please. I found a nice little tutorial for ASP.NET life cycle, but it seriously glosses over postbacks (amongst other things).
I am looking to the developers who have been around before .NET and really don't take these kinds of things for granted. Books and hyperlinks are reasonable answers or additions to your answer.
This question is related to
asp.net
The Wikipedia definition of postback is pretty good, but I'd add the following: A postback is a subsequent HTTP POST to the same page that the form is on.
If I have a page with a form on it and, rather than having my Submit button redirect the browser to another page that will process the form, instead have the Submit button refresh the current page (and perform some specific steps to validate/save the page, presumably), then that Submit button is said to have posted back to the current page.
Postbacks can be either full (refresh the entire page) or partial (in a case where AJAX is employed). A partial page postback will re-render only a part of the page (like a single drop-down list, a table, etc.).
Web developement generally involves html pages that hold forms (<form> tags). Forms post to URLs. You can set a given form to post to any url you want to. A postback is when a form posts back to it's own page/url.
The term has special significance for ASP.Net developers, because it is the primary mechanism that drives a lot of the behavior for a page -- specifically 'event handling'. ASP.Net pages have exactly one server form that nearly always posts back to itself, and these post backs trigger execution on the server of something called the Page Lifecycle.
The term is also used in web application development when interacting with 3rd party web-service APIs
Many APIs require both an interactive and non-interactive integration. Typically the interactive part is done using redirects (site 1 redirects a user to site 2, where they sign in, and are redirected back). The non-interactive part is done using a 'postback', or an HTTP POST from site 2's servers to site 1's servers.
When a script generates an html form and that form's action http POSTs back to the same form.
Yet the question is answered accurately above, but just want to share my knowledge . Postback is basically a property that we can use while doing some tasks that need us to manage the state of the page, that is either we have fired some event for e.g. a button click or if we have refreshed our page. When our page loads for the very first time , that is if we have refreshed our page, at that time postback-property is false, and after that it becomes true.
if(!ispostback)
{
// do some task here
}
else
{
//do another task here
}
http://happycodng.blogspot.in/2013/09/concept-of-postback-in.html
Web developement generally involves html pages that hold forms (<form> tags). Forms post to URLs. You can set a given form to post to any url you want to. A postback is when a form posts back to it's own page/url.
The term has special significance for ASP.Net developers, because it is the primary mechanism that drives a lot of the behavior for a page -- specifically 'event handling'. ASP.Net pages have exactly one server form that nearly always posts back to itself, and these post backs trigger execution on the server of something called the Page Lifecycle.
Postback refers to HTML forms. An HTML form has 2 methods: GET and POST. These methods determine how data is sent from the client via the form, to the server. A Postback is the action of POSTing back to the submitting page. In essence, it forms a complete circuit from the client, to the server, and back again.
The following is aimed at beginners to ASP.Net...
A postback originates from the client browser. Usually one of the controls on the page will be manipulated by the user (a button clicked or dropdown changed, etc), and this control will initiate a postback. The state of this control, plus all other controls on the page,(known as the View State) is Posted Back to the web server.
Most commonly the postback causes the web server to create an instance of the code behind class of the page that initiated the postback. This page object is then executed within the normal page lifecycle with a slight difference (see below). If you do not redirect the user specifically to another page somewhere during the page lifecycle, the final result of the postback will be the same page displayed to the user again, and then another postback could happen, and so on.
The web application is running on the web server. In order to process the user’s response, cause the application state to change, or move to a different page, you need to get some code to execute on the web server. The only way to achieve this is to collect up all the information that the user is currently working on and send it all back to the server.
Some things for a beginner to note are...
From wikipedia:
A Postback is an action taken by an interactive webpage, when the entire page and its contents are sent to the server for processing some information and then, the server posts the same page back to the browser.
A post back is round trip from the client (Browser) to the server and then back to the client.
This enables you page to go through the asp engine on the server and any dynamic content to be updated.
Postback happens when a webpage posts its data back to the same script/dll/whatever that generated the page in the first place.
Example in C# (asp.net)
...
if (!IsPostback)
// generate form
else
process submitted data;
See ASP.NET Page Life Cycle Overview on MSDN for a good general introduction about what happens when a requests hits the server.
A PostBack is any request for a page that is not the first request. A PostBack will always be in response to a user action (triggered most commonly by a Button, AutoPostBack control or Ajax).
Postback happens when a webpage posts its data back to the same script/dll/whatever that generated the page in the first place.
Example in C# (asp.net)
...
if (!IsPostback)
// generate form
else
process submitted data;
A post back is anything that cause the page from the client's web browser to be pushed back to the server.
There's alot of info out there, search google for postbacks.
Most of the time, any ASP control will cause a post back (button/link click) but some don't unless you tell them to (checkbox/combobox)
Postback refers to HTML forms. An HTML form has 2 methods: GET and POST. These methods determine how data is sent from the client via the form, to the server. A Postback is the action of POSTing back to the submitting page. In essence, it forms a complete circuit from the client, to the server, and back again.
Postback happens when a webpage posts its data back to the same script/dll/whatever that generated the page in the first place.
Example in C# (asp.net)
...
if (!IsPostback)
// generate form
else
process submitted data;
The following is aimed at beginners to ASP.Net...
A postback originates from the client browser. Usually one of the controls on the page will be manipulated by the user (a button clicked or dropdown changed, etc), and this control will initiate a postback. The state of this control, plus all other controls on the page,(known as the View State) is Posted Back to the web server.
Most commonly the postback causes the web server to create an instance of the code behind class of the page that initiated the postback. This page object is then executed within the normal page lifecycle with a slight difference (see below). If you do not redirect the user specifically to another page somewhere during the page lifecycle, the final result of the postback will be the same page displayed to the user again, and then another postback could happen, and so on.
The web application is running on the web server. In order to process the user’s response, cause the application state to change, or move to a different page, you need to get some code to execute on the web server. The only way to achieve this is to collect up all the information that the user is currently working on and send it all back to the server.
Some things for a beginner to note are...
The term is also used in web application development when interacting with 3rd party web-service APIs
Many APIs require both an interactive and non-interactive integration. Typically the interactive part is done using redirects (site 1 redirects a user to site 2, where they sign in, and are redirected back). The non-interactive part is done using a 'postback', or an HTTP POST from site 2's servers to site 1's servers.
In the old HTML, the only way to make something updated on the webpage is to resend a new webpage to the client browser. That's what ASP used to do, you have to do this thing call a "PostBack" to send an updated page to the client.
In ASP .NET, you don't have to resend the entire webpage. You can now use AJAX, or other ASP.NET controls such that you don't have to resend the entire webpage.
If you visit some old website, you would notice that once you click something, the entire page has to be refresh, this is the old ASP. In most of the modern website, you will notice your browser doesn't have to refresh the entire page, it only updates the part of the content that needs to be updated. For example, in Stackoverflow, you see the page update only the content, not the entire webpage.
From wikipedia:
A Postback is an action taken by an interactive webpage, when the entire page and its contents are sent to the server for processing some information and then, the server posts the same page back to the browser.
From wikipedia:
A Postback is an action taken by an interactive webpage, when the entire page and its contents are sent to the server for processing some information and then, the server posts the same page back to the browser.
Postback refers to HTML forms. An HTML form has 2 methods: GET and POST. These methods determine how data is sent from the client via the form, to the server. A Postback is the action of POSTing back to the submitting page. In essence, it forms a complete circuit from the client, to the server, and back again.
Expanding on the definitions given, the most important thing you need to know as a web-developer is that NO STATE IS SAVED between postbacks. There are ways to retain state, such as the Session or Viewstate collections in ASP.NET, but as a rule of thumb write your programs where you can recreate your state on every postback.
This is probably the biggest difference between desktop and web-based application programming, and took me months to learn to the point where I was instinctively writing this way.
IsPostBack is a property of the Asp.Net page that tells whether or not the page is on its initial load and if a user has perform a button on your web page that has caused the page to post back to itself.
more on ... Asp.Net ispostback()
A post back is anything that cause the page from the client's web browser to be pushed back to the server.
There's alot of info out there, search google for postbacks.
Most of the time, any ASP control will cause a post back (button/link click) but some don't unless you tell them to (checkbox/combobox)
The following is aimed at beginners to ASP.Net...
A postback originates from the client browser. Usually one of the controls on the page will be manipulated by the user (a button clicked or dropdown changed, etc), and this control will initiate a postback. The state of this control, plus all other controls on the page,(known as the View State) is Posted Back to the web server.
Most commonly the postback causes the web server to create an instance of the code behind class of the page that initiated the postback. This page object is then executed within the normal page lifecycle with a slight difference (see below). If you do not redirect the user specifically to another page somewhere during the page lifecycle, the final result of the postback will be the same page displayed to the user again, and then another postback could happen, and so on.
The web application is running on the web server. In order to process the user’s response, cause the application state to change, or move to a different page, you need to get some code to execute on the web server. The only way to achieve this is to collect up all the information that the user is currently working on and send it all back to the server.
Some things for a beginner to note are...
Simply put this by a little code. Hope it is helpful to you. When you firstly request the page url. you can view the source code of it in most browser. Below is a sample of it .
The essential of Post Back is actually call the __doPostBack which submit all the form data got from your firstly requested back to the server. (__EVENTTARGET contains the id of the control.)
<html xmlns="http://www.w3.org/1999/xhtml">
<head><title>
NHibernate Demo
</title>
<script language="javascript" type="text/javascript">
function dopost() {
__doPostBack('LinkButton1', '');
}
</script>
</head>
<body>
<h1>NHibernate Demo</h1>
<form name="ctl01" method="post" action="Default.aspx" id="ctl01">
<div>
<input type="hidden" name="__EVENTTARGET" id="__EVENTTARGET" value="" />
<input type="hidden" name="__EVENTARGUMENT" id="__EVENTARGUMENT" value="" />
<input type="hidden" name="__VIEWSTATE" id="__VIEWSTATE" value="/wEPDwUKLTMxNzcwNTYyMWRkKHoXAC3dty39nROvcj1ZHqZ5FYY=" />
</div>
<script type="text/javascript">
//<![CDATA[
var theForm = document.forms['ctl01'];
if (!theForm) {
theForm = document.ctl01;
}
function __doPostBack(eventTarget, eventArgument) {
if (!theForm.onsubmit || (theForm.onsubmit() != false)) {
theForm.__EVENTTARGET.value = eventTarget;
theForm.__EVENTARGUMENT.value = eventArgument;
theForm.submit();
}
}
//]]>
</script>
<div>
<input type="hidden" name="__VIEWSTATEGENERATOR" id="__VIEWSTATEGENERATOR" value="B2D7F301" />
<input type="hidden" name="__EVENTVALIDATION" id="__EVENTVALIDATION" value="/wEWAwKZx5vTCgKM54rGBgLM9PumD20dn9KQguomfpAOdTG0r9Psa7al" />
</div>
<a id="LinkButton1" href="javascript:__doPostBack('LinkButton1','')">LinkButton</a>
<input type="button" value="testPostBack" id="testpostback" onclick="dopost();" />
</form>
</body>
</html>
Postback is essentially when a form is submitted to the same page or script (.php .asp etc) as you are currently on to proccesses the data rather than sending you to a new page.
An example could be a page on a forum (viewpage.php), where you submit a comment and it is submitted to the same page (viewpage.php) and you would then see it with the new content added.
Postback refers to HTML forms. An HTML form has 2 methods: GET and POST. These methods determine how data is sent from the client via the form, to the server. A Postback is the action of POSTing back to the submitting page. In essence, it forms a complete circuit from the client, to the server, and back again.
Postback is a request during which ASP restores values of controls' properties from view state.
From wikipedia:
A Postback is an action taken by an interactive webpage, when the entire page and its contents are sent to the server for processing some information and then, the server posts the same page back to the browser.
When a script generates an html form and that form's action http POSTs back to the same form.
Postback is essentially when a form is submitted to the same page or script (.php .asp etc) as you are currently on to proccesses the data rather than sending you to a new page.
An example could be a page on a forum (viewpage.php), where you submit a comment and it is submitted to the same page (viewpage.php) and you would then see it with the new content added.
Yet the question is answered accurately above, but just want to share my knowledge . Postback is basically a property that we can use while doing some tasks that need us to manage the state of the page, that is either we have fired some event for e.g. a button click or if we have refreshed our page. When our page loads for the very first time , that is if we have refreshed our page, at that time postback-property is false, and after that it becomes true.
if(!ispostback)
{
// do some task here
}
else
{
//do another task here
}
http://happycodng.blogspot.in/2013/09/concept-of-postback-in.html
When a script generates an html form and that form's action http POSTs back to the same form.
ASP.Net uses a new concept (well, new compared to asp... it's antiquated now) of ViewState to maintain the state of your asp.net controls. What does this mean? In a nutshell, if you type something into a textbox or select a dropdown from a dropdownlist, it will remember the values when you click on a button. Old asp would force you to write code to remember these values.
This is useful when if a user encounters an error. Instead of the programmer having to deal with remembering to re-populate each web control, the asp.net viewstate does this for you automatically. It's also useful because now the code behind can access the values of these controls on your asp.net web form with intellisense.
As for posting to the same page, yes, a "submit" button will post to an event handler on the code behind of the page. It's up to the event handler in the code behind to redirect to a different page if needs be (or serve up an error message to your page or whatever else you might need to do).
Web developement generally involves html pages that hold forms (<form> tags). Forms post to URLs. You can set a given form to post to any url you want to. A postback is when a form posts back to it's own page/url.
The term has special significance for ASP.Net developers, because it is the primary mechanism that drives a lot of the behavior for a page -- specifically 'event handling'. ASP.Net pages have exactly one server form that nearly always posts back to itself, and these post backs trigger execution on the server of something called the Page Lifecycle.
A post back is anything that cause the page from the client's web browser to be pushed back to the server.
There's alot of info out there, search google for postbacks.
Most of the time, any ASP control will cause a post back (button/link click) but some don't unless you tell them to (checkbox/combobox)
Expanding on the definitions given, the most important thing you need to know as a web-developer is that NO STATE IS SAVED between postbacks. There are ways to retain state, such as the Session or Viewstate collections in ASP.NET, but as a rule of thumb write your programs where you can recreate your state on every postback.
This is probably the biggest difference between desktop and web-based application programming, and took me months to learn to the point where I was instinctively writing this way.
A post back is anything that cause the page from the client's web browser to be pushed back to the server.
There's alot of info out there, search google for postbacks.
Most of the time, any ASP control will cause a post back (button/link click) but some don't unless you tell them to (checkbox/combobox)
When a script generates an html form and that form's action http POSTs back to the same form.
The following is aimed at beginners to ASP.Net...
A postback originates from the client browser. Usually one of the controls on the page will be manipulated by the user (a button clicked or dropdown changed, etc), and this control will initiate a postback. The state of this control, plus all other controls on the page,(known as the View State) is Posted Back to the web server.
Most commonly the postback causes the web server to create an instance of the code behind class of the page that initiated the postback. This page object is then executed within the normal page lifecycle with a slight difference (see below). If you do not redirect the user specifically to another page somewhere during the page lifecycle, the final result of the postback will be the same page displayed to the user again, and then another postback could happen, and so on.
The web application is running on the web server. In order to process the user’s response, cause the application state to change, or move to a different page, you need to get some code to execute on the web server. The only way to achieve this is to collect up all the information that the user is currently working on and send it all back to the server.
Some things for a beginner to note are...
Postback is essentially when a form is submitted to the same page or script (.php .asp etc) as you are currently on to proccesses the data rather than sending you to a new page.
An example could be a page on a forum (viewpage.php), where you submit a comment and it is submitted to the same page (viewpage.php) and you would then see it with the new content added.
Web developement generally involves html pages that hold forms (<form> tags). Forms post to URLs. You can set a given form to post to any url you want to. A postback is when a form posts back to it's own page/url.
The term has special significance for ASP.Net developers, because it is the primary mechanism that drives a lot of the behavior for a page -- specifically 'event handling'. ASP.Net pages have exactly one server form that nearly always posts back to itself, and these post backs trigger execution on the server of something called the Page Lifecycle.
POSTBACK: Part of ASP.NET's contrived technique for hiding the true stateless nature of the web/HTTP behind a stateful facade. This results in complex code (IsPostback, ...), a hard to understand page lifecycle, many different events, ... and numerous problems (ViewState size, web-farm stickyness, state servers, browser warnings (not using PRG pattern), ...)
See ASP.NET MVC instead.
Expanding on the definitions given, the most important thing you need to know as a web-developer is that NO STATE IS SAVED between postbacks. There are ways to retain state, such as the Session or Viewstate collections in ASP.NET, but as a rule of thumb write your programs where you can recreate your state on every postback.
This is probably the biggest difference between desktop and web-based application programming, and took me months to learn to the point where I was instinctively writing this way.
Postback happens when a webpage posts its data back to the same script/dll/whatever that generated the page in the first place.
Example in C# (asp.net)
...
if (!IsPostback)
// generate form
else
process submitted data;
Expanding on the definitions given, the most important thing you need to know as a web-developer is that NO STATE IS SAVED between postbacks. There are ways to retain state, such as the Session or Viewstate collections in ASP.NET, but as a rule of thumb write your programs where you can recreate your state on every postback.
This is probably the biggest difference between desktop and web-based application programming, and took me months to learn to the point where I was instinctively writing this way.
Source: Stackoverflow.com