Please master to explain the meaning of IsPostBack ()

wanderwb

I now think that the request for the .aspx page, if it is not modified and just browsed, is IsPostBack () == false no matter how many times, only when the user modifies the page (such as filling forms, entering data, etc.), the server sends back It will be IsPostBack () == true. I wonder if this understanding is correct? I would like to know under what circumstances will it be! IsPostBack (), and under what circumstances will it be IsPostBack (). Thank you!

yfacmilan

The first time to open and refresh are: not IsPostBack

yfacmilan

Perform a background action, the server sends back, which is IsPostBack

xiaoren6412

Open the page for the first time: The value of IsPostBack () is false;
Back to the server, IsPostBack () becomes true;
! Is negated, generally
if (! IsPostBack)
{
// Represents the first page read
}
else
{
  // Return the code in the future
}

dydcool

To put it bluntly, when you enter the page, go to if (! IsPostBack), then after your page refreshes (submitted to the server, etc.), you will not go

wanderwb

Please explain further:
return?
Postback?
Callback?

Who is it to whom, who to whom and who to call? Thank you!

牧野鹰扬

xiaoren6412
correct

saintfrosty

Open the client source code of your asp.net page, you will see a
  <input type = "hidden" name = "__ VIEWSTATE" id = "__ VIEWSTATE" .... />
Field, this is the source of the IsPostback function.

When the page is requested with the http Post command and the parameter contains this __VIEWSTATE, the page's IsPostback == true.

Both Postback and Callback are IsPostback == true. In the latter case, the difference between callback and postback can be further distinguished by the IsCallback function of the page.

feelair

Thank you all
Before, I only knew whatxiaoren6412said
Open the page for the first time: the value of IsPostBack () is false;
Back to the server, IsPostBack () becomes true;
! Is negated, generally
if (! IsPostBack)
{
// Represents the first page read
}
else
{
  // Return the code in the future
}
  
It ’s really beneficial to come here often! !

wanderwb

So, what is the difference between Request and Postback?