I use ASP.NET and have a label control on my page, which I fill with
the jQuery-Command
$('#<%= myLabel.ClientID %>').html(content);
.val() does not seem to work with this.
Somehow, I have Problems getting the content in code-behind. In the code, the myLabel.Text-Property is still empty.
If you want to display the value on the client and have it available on the page, you need an input that'll get sent to the code-behind when you POST like this:
$('#<%= myLabel.ClientID %>').html(content);
$('#<%= myInput.ClientID %>').val(content);
<asp:Label Id="myLabel" runat="server" />
<asp:HiddenField ID="myInput" runat="server" />
In the code-behind:
myInput.Value
I think your problem is that labels (rendered as span tags) are inherently read-only in the asp.net world. They're not meant to be used as 'input' controls, and as such changes to their HTML on the client-side are ignored on the server-side, where values are set based on ViewState.
To do what you are asking, you'd have to notify the server of the change as well, such as by using AJAX. The only issue here is ajax webmethods in your code behind are static, and because of this can't access the page's control set to change the .Text value.
In the end the easiest option is to make use of hidden fields as Nick said. These are technically 'input' controls and their values changed on the client-side are sent to the server as you desire. You'd just have to keep the label/span and hidden field/input synchronized on the client.
Hope this helps.
Related
I put an asp.net hiddenfield into one of my pages. I couldn't access it through javascript and when I went to view source, I couldn't find it in the page at all. Is there any obvious reason for this?
Here's the line with the hidden field:
<asp:HiddenField ID="HiddenEmailAddress" runat="server" Value="test" />
The problem was that the hiddenfield was placed in a table that was invisible at the time. Will self answer when system allows.
Your control is inside of another control that has it's visibility set to false, but you already knew that. :D
When don't you need to use runat="server" in ASP.NET?
EDIT: Thanks for all the answers, but I was really thinking of runat="server" inside an <asp: tag.
Use the runat=server attribute when you're using ASP.NET controls, and/or you require programmatic access to those controls in your code-behind.
HTML controls don't require this attribute. It's useful if you have any HTML element like <span> <div>, or <table> when you want the ability to access them in code-behind.
<asp:Label runat="server" id="foo" />
<div runat="server" id="bar />
...
foo.Text = "Hello Label";
foo.Attributes["class"] = "baz";
You need to use runat="server" on any control that you want to be parsed as a server control.
Any element with runat="server" will be parsed into a server control in the Page herarchy. Anything else will be handled as plain text, and put in LiteralControl controls in the Page hierarchy.
The exception is elements that aren't real elements, but special tags within another server tag, for example ContentTemplate tags. They don't need a runat="server" because the containing control will parse them.
When you don't want the server side ASP.NET to render a server side variable against us.
Generally speaking you don't use it when you don't need to manipulate the DOM element at the server side e.g. which are only used for layout purposes.
Without runat="server" there would also be no other way to make html controls server side controls. It does look like an odd thing, because you can't do runat="client".
So in summation you can't leave it out on any ASP .Net controls ever and it was probably the easiets and cleanest way to find all server side controls for the developers who created ASP .Net Web forms.
source: http://mikeschinkel.com/blog/whyrunatserverforaspnetpart2/
Tag runat="server" indicates that the code contained within the script block will run on the server (and not on the client). On execution, ASP.NET will create server-side objects that contain this code as well as an instance of the Page class to contain the controls defined inside the page as instances of their given type (System.Web.UI.WebControls.Textbox, for example). This server-side object will be invoked on user request and will execute code in response to events.
Create Control in Runtime
I need one label in runtime that time don't need runat="Server" is not required
Example
protected void Page_Load(object sender, EventArgs e)
{
if (!IsPostBack)
{
Label lblNew = new Label();
lblNew.ID ="lblnew";
lblNew.Text ="Test";
}
}
this code create label in runtime at page load event
It seems everyone is doing this (in code posts etc.)...but I don't know how. :(
Whenever I try to manipulate an asp element using JavaScript I get an "element is null" or "document is undefined" etc. error.....
JavaScript works fine usually,...but only when I add the runat="server" attribute does the element seem invisible to my JavaScript.
Any suggestions would be appreciated.
Thanks, Andrew
What's probably happening is that your element/control is within one or more ASP.NET controls which act as naming containers (Master page, ITemplate, Wizard, etc), and that's causing its ID to change.
You can use "view source" in your browser to confirm that's what's happening in the rendered HTML.
If your JavaScript is in the ASPX page, the easiest way to temporarily work around that is to use the element's ClientID property. For example, if you had a control named TextBox1 that you wanted to reference via JS:
var textbox = document.getElementById('<%= TextBox1.ClientID %>');
Making an element runat="server" changes the client-side ID of that element based on what ASP.NET naming containers it's inside of. So if you're using document.getElementById to manipulate the element, you'll need to pass it the new ID generated by .NET. Look into the ClientId property to get that generated ID...you can use it inline in your Javascript like so:
var element = document.getElementById('<%=myControl.ClientID%>');
If you have a textbox:
<asp:TextBox id="txtText" runat="server" />
YOu can use:
var textBox=document.getElementById('<%=txtText.ClientID %>');
Any WebControl exposes the same ClientID property.
All though the question has been answered, thought I would just post some further info...
Rick Strahl provided quite an intresting work around to this problem.
http://www.west-wind.com/WebLog/posts/252178.aspx
Thankfully when ASP .NET 4.0 arrives, it will allow you to specify exacly what the client ID's will be!
http://www.codeproject.com/KB/aspnet/ASP_NET4_0ClientIDFeature.aspx
The following .NET 3.5 code, placed in an aspx file, will trigger a JavaScript error when the page is loaded (for users who have JavaScript enabled):
<noscript>
<asp:TextBox ID="txt" runat="server"></asp:TextBox>
<asp:RequiredFieldValidator ID="txt_RequiredFieldValidator" runat="server"
ControlToValidate="txt"></asp:RequiredFieldValidator>
<asp:Button ID="btn" runat="server" Text="Button" />
</noscript>
The error happens because the JavaScript generated by the ASP.NET validator control does not contain a null check on before the second code line below:
var ctl00_body_txt_RequiredFieldValidator =
document.all ?
document.all["ctl00_body_txt_RequiredFieldValidator"] :
document.getElementById("ctl00_body_txt_RequiredFieldValidator");
ctl00_body_txt_RequiredFieldValidator.controltovalidate = "ctl00_body_txt";
Can anyone suggest a workaround to this?
Footnote: Why am I doing this? For my non-JavaScript users I am replacing some AJAX functionality with some different UI components, which need validation.
You should add the following to the RequiredFieldValidator:
enableclientscript="false"
Seeing as you are using these in <noscript> tags, there is no point in supplying client side vaildation of the controls - they are only going to display if JS is turned off.
This will force the validation to happen (automatically) on the server side for you.
Just make sure you call "Page.IsValid" before you process the response.
See BaseValidator.EnableClientScript for more details.
The javascript is looking for an element contained in the noscript? AFAIK there's no clean way to detect script support from the server side.
I think you'll need to build in a redirect (I've seen this done with a meta-refresh in a header noscript if you don't mind a validation failure) to push noscript users to a "please turnscript on page" or do some surgery to loosen up the validation/control binding which may take some amount of wheel reinventing. This is one of those areas where asp.net's tight coupling between controller and view really punishes.
I need help on this following aspx code
aspx Code:
<asp:Label ID ="lblName" runat ="server" Text ="Name"></asp:Label>
<asp:TextBox ID ="txtName" runat ="server"></asp:TextBox>
Consider this is my aspx page content. I am going to populate the values for the TextBox only after the postback from server. But the label is also posting to the server (runat="server") even though it's not necessary. Should I write my code like this to save time from server with less load.
Corrected Code:
<label id ="lblNames">Name</label>
<asp:TextBox ID ="txtName" runat ="server"></asp:TextBox>
Only my server control will send to the server for postback and not my HTML control which has a static value.
Please suggest whether this is the correct way of coding.
If you take the runat='server' out of the <label> element then it won't be parsed as a server control. If you're not going to do anything with lblNames from the server then it is perfectly okay to leave it out.
If you're not doing anything with the label server-side, then just use a <span>. It'll end up as the same html at the browser.
.net label controls are rendered as html label elements and do not get posted back to the server. Labels just don't post back. The server control allows you to manipulate the properties of the control in code however which is very useful.
There is nothing wrong with using html tags as well in your aspx/ascx page though if you don't need any programmatic control of the element.