ASP.NET

25-Feb-07 2:54

Is it possible to check the value of a user control, used on a website by means of a client script on that website. I think it should be of cource, but the 'element.value' notation doesn't work. My user control contains a listbox, initialized in the user control's code. What I'm doing wrong?

Wilfried

Guffa25-Feb-07 3:47

25-Feb-07 3:47

View the source of the page, and you will see that the id of the element is not just "element", but the name of other controls has been prepended to the name.

Use the ClientID property to get the full id that you can use in client code.

I recommend that you use the document.getElementById method instead of just referring to the elements as if they were global variables. It works in most browser in most of the cases, but not always.

A common shorthand for the getElementById is the $ function:

function $(id) { return document.getElementById(id); }

---
single minded; short sighted; long gone;

wilf5725-Feb-07 23:12

25-Feb-07 23:12

Thanks for answering.

Sorry probably my description was not precise. I used the normal access methods already. My user control has the ID sodatum, so I try to access it by:

sodatum.value or
document.getElementById("sodatum").value

but it both returns null. There is another textbox on the same page, named 'artnr' and even another listbox too, both of them accessible.

It must be, because it's a user control. It's implemented in the following way:

<%@ Register TagPrefix="ucSod" TagName="sodat" Src="~/uc/sodatum.ascx" %>
<%@ Page Language="VB" CodeFile="Suche.aspx.vb" Inherits="Suche" %>

<script type ="text/ecmascript">
    alert(document.getElementById("artnr").value;
    alert(document.getElementById("sodatum").value;
</script>

<form id="frmSuchen" runat="server" method="post">
|asp:TextBox ID="artnr" runat="server" </asp:TextBox>
|ucSod:sodat ID="sodatum" runat="server"/>
</form>

I used '|' instead of '<' here, because otherwise it's not properly displayed in this forum message. In the code there are '<' of course.
The first alert works, the second doesn't.

Wilfried

Guffa26-Feb-07 15:12

Re: ASP user control and client scripting [modified]

26-Feb-07 15:12

wilf57 wrote:
The first alert works, the second doesn't.

No, neither of them works. The first alert shows the value of the 'artnr' textbox in the page, not the 'artnr' textbox in the user control.

---
single minded; short sighted; long gone;

wilf5726-Feb-07 3:28

26-Feb-07 3:28

So I found the sh*t myself
asp.net renders a user control differnt than a normal control. The ID of a user control on the webpage is a combination of the ID used on the page and that in the user control HTML code.
Best way: look at the source code of the page created by asp.net and wich ID asp.net used to address the specific control.
Ex.
If the user control is implemented the following way:

|ucSod:sodat ID="sodatum" runat="server"/>

client script access is thru: formxxx.sodatum_sodat.value
(there's a '<' instead of the '|', but then it's not displayed in the forum, why???

-- modified at 9:36 Monday 26th February, 2007

Guffa26-Feb-07 15:09

26-Feb-07 15:09

wilf57 wrote:
So I found the sh*t myself
asp.net renders a user control differnt than a normal control. The ID of a user control on the webpage is a combination of the ID used on the page and that in the user control HTML code.

I told you so. Didn't you read my post before you replied to it?

Best way: look at the source code of the page created by asp.net and wich ID asp.net used to address the specific control.

No, the best way is to use the ClientID property, just as I wrote in my previous post. The way that the id is created may change with the version of framework, but the ClientID property will always return the correct id.

---
single minded; short sighted; long gone;

wilf5728-Feb-07 9:44

28-Feb-07 9:44

the last one is an argument, but still:
if there is a user control on the page like this:
<ucSod:sodat ID="sodatum" runat="server"/>

then
document.getElementById("sodatum").value
doesn't work

what works is:
document.getElementById("sodatum_sodat").value

try it (I'm using ie6)

for me it seems logical, because if the control's ID in the server produced HTML code is 'sodatum_sodat' any javascript cannot access the control by 'sodatum'

Guffa1-Mar-07 6:01

Re: ASP user control and client scripting [modified]

1-Mar-07 6:01

You are completely missing the point.

Use the ClientID property to get the name to use in the client code.

If you hard code the name, your code only works with the exact structure that your page has. If anything changes in that structure, the name changes. Also, you can only use the code for that single page, you can't put the user control in another page if it doesn't have the exact same structure.

Also, if you deply the application to a web server, it's not certain that it will use the same pattern to create the name. An update of IIS or the framework may also change the way that the name is constructed.

---
single minded; short sighted; long gone;

wilf572-Mar-07 3:35

2-Mar-07 3:35

Ok I got that. I read about it in the help too.

<form id="frmSuchen" runat="server" method="post">
<asp:TextBox ID="artnr" runat="server"></asp:TextBox>
<ucSod:sodat ID="sodatum" runat="server"/>
</form>

Now I tried this in the client script:
document.getElementById("<%=artnr.ClientID%>").value
document.getElementById("<%=sodatum.ClientID%>").value

the first statement with the textbox works fine, the second one with the user control doesn't it says:

document.getElementById("<%=sodatum.ClientID%>")is not an object.
and indeed when I execute on the server side (in page_load() or even aftzer loading in a button event:
Msgbox me.sodatum.ClientID
it always prints 'sodatum' and not 'sodatum_sodat' as I'd have expected.

any explainations?

Thanks for your patience

Wilfried

Guffa2-Mar-07 8:36

2-Mar-07 8:36

Is the client script inside the user control? Otherwise you can not reference the controls in that way, you have to specify that they are in the user control. You also have to change their accessibility to public, or expose them through public properties in the user control.

Are you sure that the first one works correctly? Do you get the value from the field in the user control and not the field in the page?

---
single minded; short sighted; long gone;

wilf572-Mar-07 11:31

2-Mar-07 11:31

The first one is simply a textbox on the page. Thats why it works fine.
The client script is on the page, not in the user control.
I wrote a public property (Text) in the user control, so I can read and write the listbox(the one in the user control) on the server side but that doesn't help on the page client side, right?!
So you say in the page client script I cannot access the listbox inside the user control by its ClientID property , only by the hard coded ID.

Ok next week I'm going skiing, I have do deal with that thing after that.
Thanks again

Wilfried

Guffa2-Mar-07 14:11