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aspdotnet_website_programming thread: Trying to implement the Chapter 4 trick (Javascript Prompt ).

Message #1 by "CotasseWrox" <ocotasson@n...> on Thu, 23 May 2002 11:57:23
Hello code-fellows . 

I do appreciate the trick explained in chapter 4 regarding the "Javascript 
Prompt" that eventually triggers a server-side validation (those who read 
the Book know what I am talking about). 

This code snippet is quite handy, I tried to test it on a blank page. 
Unfortunately it doesn't work. Please have a look at my code below. You 
may even test it on your computer (no codebehind or inheritance involved). 

Generated page can be seen at : 

Here's what it should do : 

When you click on the "ok" button, the Javascript function tests whether 
the TextBox was filled in.
If not then 
 just start an "alert();" message. 
 trigger the __doPostBack('btn2','');
end if 

But the latter part doesn't work...

However if 
-I replace __doPostBack('btn2',''); by my (pure client-side) __doPostBack2
('btn2',''); function it works. 

-I type javascript:__doPostBack('btn2','') in the address bar it also 
works (server-side function). 

-for demo purpose I specified the Text attribute (value=test3) of 
my "btn2" button. When I click this link, it also work. 

Any idea, anyone ? 

Here is the code : 

<%@ Page Language=C#%>
<script runat=server>
	void Page_Load(Object sender, EventArgs e){
		if (!IsPostBack){

	void btn2_Click	(Object sender, EventArgs e){


<script language=Javascript>
function btn2(){
		alert("field cannot be left empty!");

function __doPostBack2(zeString,zeVal){
alert("zeString "+zeString);


<form id=myForm runat=server>
	<asp:TextBox  id=txt1 runat=server/>
	<asp:Button Text=Ok id=btn1 runat=server/>
	<asp:Label id=lbl1 runat=server/>
	<asp:LinkButton text="test3" ID="btn2" runat="server" 
OnClick="btn2_Click" />

Thanx for reading!

Message #2 by "CotasseWrox" <ocotasson@n...> on Thu, 23 May 2002 14:14:46
For those it may concerns : I found the reason why...

You cannot add Javascript attributes to a Web Control if you wanna use 
this trick. 

Use a normal (i.e. plain) HTML control. 
That is : 
<a href="javascript:Btn2()">This Will work</A> 



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