A Question about Events

[DC]

In a book sample I am working through in ASP.NET, a simple Hello World works
fine, but the order of events has me confused.

The sample involves a Button control and the onClick event. On click, the
page reloads and voila, hello world is written (I understand this part).

However, when I set a breakpoint on both Page_Load and onClick, Page_Load is
accessed first, stepping through takes me to onClick.

But "Hello World" is written outside of all HTML elements. I was under the
impression that on Page_Load the HTTP stream is persisted until processing
of events is completed, so why isnt Hello World written in the HTML elements
(specifically, the BODY tag)?

Thank you!

 

[Cowboy]

The HTML tags are processed after the load. I am not sure which book you are
working with, but it is a bad ASP.NET example (many are). As ASP.NET works
on a binding model, you are best to place a container (a panel comes to
mind) on the page and add controls (for plain text, use a LiteralControl).

Page_Load runs every time the page loads. So, it is natural it will run
every time. It is not a great event to slap in a bunch of stuff; use the
button event instead. The normal signature should be something like:

protected void Page_Load(object sender, EventArgs e)
{
if(!Page.IsPostback)
{
//Something that runs on a hit without a postback
}
else
{
//Code that runs EVERY time a page is posted back to
//NOTE: Do not make a conditional tree here,
// use the postback events instead
}
}

In most books, you see the horrible code tree like:

if(!Page.IsPostback)
//set up initial page
else
if condition1
// lots of code here
else if condition 2
//lots of code here
else
//lots of code here

protected void btnWhatever_Click(object sender, EventArgs e)
{
//empty routine
}

--
Gregory A. Beamer
MVP; MCP: +I, SE, SD, DBA

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