ASP.NET - Events
An Event Handler is a subroutine that executes code for a given event.
ASP.NET - Event Handlers
Look at the following code:
<%
lbl1.Text="The date and time is " & now()
%>
<html>
<body>
<form runat="server">
<h3><asp:label id="lbl1" runat="server" /></h3>
</form>
</body>
</html> |
When will the code above be executed? The answer is: "You don't know..."
The Page_Load Event
The Page_Load event is one of many events that ASP.NET understands. The Page_Load event is triggered when a page loads, and ASP.NET will automatically
call the subroutine Page_Load, and execute the code inside it:
Example
<script runat="server">
Sub Page_Load
lbl1.Text="The date and time is " & now()
End Sub
</script>
<html>
<body>
<form runat="server">
<h3><asp:label id="lbl1" runat="server" /></h3>
</form>
</body>
</html>
|
Show example »
|
Note: The Page_Load event contains no object references or event
arguments!
The Page.IsPostBack Property
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):
Example
<script runat="server">
Sub Page_Load
if Not Page.IsPostBack then
lbl1.Text="The date and time is " & now()
end if
End Sub
Sub submit(s As Object, e As EventArgs)
lbl2.Text="Hello World!"
End Sub
</script>
<html>
<body>
<form runat="server">
<h3><asp:label id="lbl1" runat="server" /></h3>
<h3><asp:label id="lbl2" runat="server" /></h3>
<asp:button text="Submit" onclick="submit" runat="server" />
</form>
</body>
</html>
|
Show example »
|
The example above will write the "The date and time is...." message only the
first time the page is loaded. When a user clicks on the Submit button, the
submit subroutine will write "Hello World!" to the second label, but the date
and time in the first label will not change.
Make your web applications look like a million bucks
|
|
Most web applications today use boring methods to present data to their viewers using grids or simple HTML tables. FusionCharts induces "life" into the web applications by converting monotonous data into lively charts, gauges & maps.
FusionCharts works with all technologies like ASP, ASP.NET, PHP, ColdFusion, Ruby on Rails, JSP, HTML pages etc.
and connects to any database to render animated & interactive charts. It takes less than 15 minutes and no expertise
whatsoever to build your first chart and just a glance of it to captivate your audience. This fact is endorsed by our
12,000 customers and 150,000 users which include a majority of the Fortune 500 companies.
And yeah, your applications could look like a million bucks by spending just $69.
So go ahead, download your
copy of FusionCharts and start "wow-ing" your customers now!
|
 |
W3Schools' Online Certification Program
The perfect solution for professionals who need to balance work, family, and career building.
More than 4000 certificates already issued!
|
The HTML Certificate documents your knowledge of HTML, XHTML, and CSS.
The JavaScript Certificate documents your knowledge of JavaScript and HTML DOM.
The XML Certificate documents your knowledge of XML, XML DOM and XSLT.
The ASP Certificate documents your knowledge of ASP, SQL, and ADO.
The PHP Certificate documents your knowledge of PHP and SQL (MySQL).
|