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What is IsPostBack


Posted Date: 10 Jul 2008      Posted By:: Radhey Shyam     Member Level: Bronze    Member Rank: 0     Points: 1   Responses: 8



What is the ispostback property of the page.Where we used !ispostback?



Responses

#261899    Author: sivangari      Member Level: Gold      Member Rank: 0     Date: 10/Jul/2008   Rating: 2 out of 52 out of 5     Points: 6

hi,
Page.IsPostBack Is used to check if the user posted back to the page. Meaning they clicked a button or changed a field in the form that causes it to post back to itself.
Putting Not usually is used to check the initial load of the page.
You only need to fill databound fields on the initial load, so you put all your databinding code in the Not page.IsPostBack. The values are saved in the viewstate and can only be read by the form if it gets posted back to itself.
So, if it is a postback dont do databinding if its not a postback do databinding.


 
#261903    Author: VMRK      Member Level: Gold      Member Rank: 1887     Date: 10/Jul/2008   Rating: 2 out of 52 out of 5     Points: 4

If not postback is the function which is used in the pageload eveent to know that this s the first time the page is initiated
so watever u wnat to display in the frst run should be put in within this code

there are some items whch needs to be shown everytime when u come back to the page
so have that in the else block


 
#261908    Author: Subhi      Member Level: Gold      Member Rank: 336     Date: 10/Jul/2008   Rating: 2 out of 52 out of 5     Points: 6

Returns a value indicating whether the page is being loaded in
response to a client postback, or if it is being loaded and
accessed for the first time.

Syntax

Script [ bool variable = ] Page.IsPostBack

Property Value

This property returns only a boolean value: true if the page is
being loaded in response to a client postback; otherwise, false.
Default value is false.
Remarks

Use the IsPostBack property to test either of two states:


1. if the page is being loaded and accessed for the first time
( IsPostBack returns false ), or
2. if the page is being loaded in response to a client
postback ( IsPostBack returns true ).

This property is typically used within a Page_Load event handler
to conditionally execute one or more embedded statements,
depending on the IsPostBack state when the page is loaded.

Example

The following example evaluates IsPostBack on page load, and runs
the embedded statements only if IsPostBack is not true,
indicating the page is being accessed for the first time.


protected void Page_Load ( Object Src, EventArgs E ) {
if ( !IsPostBack ) {
string query = "SELECT distinct Type FROM Products";
mySelect.DataSource = fetchData ( query, "gear" );
mySelect.DataBind ( );
}
}





 
#261910    Author: Ratheesh      Member Level: Gold      Member Rank: 721     Date: 10/Jul/2008   Rating: 2 out of 52 out of 5     Points: 1

The Page_Load subroutine runs EVERY time the page is loaded. If you want to execute the code in the Page_Load subroutine only the FIRST time the page is loaded, you can use the Page.IsPostBack property. If the Page.IsPostBack property is false, the page is loaded for the first time, if it is true, the page is posted back to the server
Syntax

Script [ bool variable = ] Page.IsPostBack


Property Value
This property returns only a boolean value: true if the page is being loaded in response to a client postback; otherwise, false. Default value is false.

Remarks
Use the IsPostBack property to test either of two states:

if the page is being loaded and accessed for the first time ( IsPostBack returns false ), or
if the page is being loaded in response to a client postback ( IsPostBack returns true ).
This property is typically used within a Page_Load event handler to conditionally execute one or more embedded statements, depending on the IsPostBack state when the page is loaded.

Example
<%@ Page Language="vb" %>
<html>
<head>
<title>IsPostBack property example</title>
<script runat="server">
Sub Page_Load()
If Page.IsPostBack Then
Message.Text = "PostBack"
Else
Message.Text = "Non-PostBack"
End If
End Sub
</script>
</head>
<body>
<form runat="server">
<asp:button id="post" Text="Post page" runat="server"/>
<asp:label id="Message" runat="server"/>
</form>
</body>
</html>


 
#261914    Author: yeshu      Member Level: Gold      Member Rank: 1769     Date: 10/Jul/2008   Rating: 2 out of 52 out of 5     Points: 5

The property gets a boolean value indicating whether the page is being loaded in response to a client postback, or if it is being loaded and accessed for the first time.

Uses:
For example you want to load a dropdown list only once i.e only for the first request then give the condition !IsPostBack()
and load the dropdown list.

This makes sure that the dropdown list is not loaded each and everytime when the page is requested or posted back.


 
#262063    Author: Nithya      Member Level: Gold      Member Rank: 778     Date: 10/Jul/2008   Rating: 2 out of 52 out of 5     Points: 6

hi...

Page.IsPostBack Is used to check if the user posted back to the page. Meaning they clicked a button or changed a field in the form that causes it to post back to itself.
Putting Not usually is used to check the initial load of the page.
You only need to fill databound fields on the initial load, so you put all your databinding code in the Not page.IsPostBack. The values are saved in the viewstate and can only be read by the form if it gets posted back to itself.
So, if it is a postback dont do databinding if its not a postback do databinding


 
#262109    Author: Kumar Velu      Member Level: Gold      Member Rank: 122     Date: 10/Jul/2008   Rating: 2 out of 52 out of 5     Points: 6

Page.IsPostBack Is used to check if the user posted back to the page. Meaning they clicked a button or changed a field in the form that causes it to post back to itself.
Putting Not usually is used to check the initial load of the page.

This property is used to check whether the page is being loaded and accessed for the first time or whether the page is loaded in response to the client postback.
Example:
Consider two combo boxes
In one lets have a list of countries
In the other, the states.
Upon selection of the first, the subsequent one should be populated in accordance. So this requires postback property in combo boxes to be true.


 
#263476    Author: Ashok Khanna      Member Level: Gold      Member Rank: 266     Date: 15/Jul/2008   Rating: 2 out of 52 out of 5     Points: 1

Page.IsPostBack Property

Gets a value indicating whether the page is being loaded in response to a client postback, or if it is being loaded and accessed for the first time.

The Page_Load subroutine runs EVERY time the page is loaded. If you want to execute the code in the Page_Load subroutine only the FIRST time the page is loaded, you can use the Page.IsPostBack property. If the Page.IsPostBack property is false, the page is loaded for the first time, if it is true, the page is posted back to the server (i.e. from a button click on a form)

Use the Page.IsPostBack property to ensure that you only perform page initialization logic when a page is first loaded and not in response to client postbacks.

Please rate this post, if it is useful for you.

Thanks & Regards
Ashok


 
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