What is use of IsPostBack in ASP.NET

Question

Hi Friends

I want to know what is use of IsPostBack property in asp.net and why we use this property. If we don't use IsPostBack property then what will effect ? Please tell me anyone IsPostBack property in details with example ?

Thanks

Krunal Rohit · Answer

When does it happen? 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. What happens? 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. Why does it happen? 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 state of the controls on the posting back page are available within the context. This will allow you to manipulate the page controls or redirect to another page based on the information there. Controls on a web form have events, and therefore event handlers, just like any other controls. The initialisation part of the page lifecycle will execute before the event handler of the control that caused the post back. Therefore the code in the page's Init and Load event handler will execute before the code in the event handler for the button that the user clicked. The value of the "Page.IsPostBack" property will be set to "true" when the page is executing after a postback, and "false" otherwise. Technologies like Ajax and MVC have changed the way postbacks work.

venkata kumar · Answer

hi what ever code u written in ispostback method. that will work only once when browser load irst time. Thanks & Regards Ravi

Satish Maddula · Answer

For example if you are loaded dropdown list in pageload event if you change the drop down again request went to webserver and coming to client it displays same data alreday data is populated how man times you change the drop down same data will be populated that means duplicate data.

Shubham Saini · Answer

Is Postback is normally used on page _load event to detect if the web page is getting generated due to postback requested by a control on the page or if the page is getting loaded for the first time.

Vineet Kumar Saini · Answer

Thanks to all my friends.

Satyapriya Nayak · Answer

Page object has a IsPostBack property which can be checked to know that is the page posted back.The Page_Load event handler in the page checks for IsPostBack property value, to ascertain whether the page is posted. The Page.IsPostBack gets a value indicating whether the page is being loaded in response to the client postback, or it is for the first time. The value of Page.IsPostBack is True, if the page is being loaded in response to the client postback; while its value is False, when the page is loaded for the first time. The Page.IsPostBack property facilitates execution of certain routine in Page_Load, only once (for e.g. in Page load, we need to set default value in controls, when page is loaded for the first time. On post back, we check for true value for IsPostback value and then invoke server-side code to update data).

Vineet Kumar Saini · Answer

Hi nayak ji, I already read this but I not understand.

Satyapriya Nayak · Answer

Gets a value that indicates whether the page is being rendered for the first time or is being loaded in response to a postback. http://www.codeproject.com/KB/aspnet/IsPostBack.aspx

What is use of IsPostBack in ASP.NET

Answers (8)