I have some code on a User Control that looks like this:
<asp:PlaceHolder id="ph1" runat="server">
<script type="text/javascript">
jQuery(function() {
doSomethingAwesome();
});
</script>
</asp:PlaceHolder>
I want to get the contents of the PlaceHolder control. I'm trying to get it in the OnPreRender of the page this control is on. I would have expected that the contents of the PlaceHolder would be be a single Literal control, but the Controls collection is empty.
How can I get the contents of the PlaceHolder control on the server side?
Literal content doesn't exist on the server because it's not in a server control.
If you need to make the script visible on the server, you'll need to explicitly put it inside a server control with the "runat=server" property set.
To get contents on client side you can do
$('#ph1').html()
If using naming containers which is likely because of user controls
$('#<%=ph1.ClientID%>').html()
Related
I am having a bootstrap problem I hope one of you might have a solution to.
I have placed all my JavaScript references in the bottom of my masterpage. This usually works fine, but now I have a ASCX control which needs to add some JavaScript too the footer (initialization of a module). The reason why I can't initialize the module from the master page is because I need some properties from my codebehind file.
In ASP.NET MVC I would have used sections to inject data from a usercontrol to a section in the masterpage, but is this even possible in ASP.NET Webforms 4?
No, that concept of sections in not available in WebForms.
One way to do what you've described is to use the <%= %> syntax and send the values of server properties to the client (HTML output). In your ASCX control you can have the following markup:
<script type="text/javascript">
var clientProperty = <%= MyServerProperty %>;
</script>
ASP.NET WebForms will substitute the value of MyServerProperty above when it renders the page, and then you can access clientProperty as a global variable from the script in the masterpage.
Another approach is to use a Hidden field and set its value on the server. It will be rendered as an <input type="hidden">, whose value you can then get from any script by ID.
A third option is to load the actual client script only from the ASCX control (when it makes sense), rather than put it in the masterpage (when it will be loaded everywhere in the site).
You could add something like this to the bottom of your master page:
<asp:PlaceHolder runat="server" ID="javascriptSection" />
Then in your page's code behind or in a <% %> tag:
var scriptTag = new HtmlGenericControl("script");
scriptTag.Attributes["type"] = "text/javascript";
scriptTag.InnerHtml = #"function () { ... }";
var javascriptSection = this.Page.Master.FindControl("javascriptSection");
if (javascriptSection != null)
javascriptSection.Controls.Add(scriptTag);
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
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.
When coding an Asp.Net page, you generally add a runat attribute in the aspx:
<form id="form1" runat="server">
Is it possible to tell in the code behind if the user hasn't done this i.e. they only did this:
<form id="form1">
Here the form has the id "form1" but in my case I don't know this. Code behind such as this is what I am looking for:
if(Page.HasForm)
{
}
You can only ever have one form tag with "runat=server" on it per .aspx page. All you have to do is to check to see if Page.Form is null or not. If it's null, then there's no form that has been marked to runat server.
if (Page.Form != null)
{
}
It's the runat="server" part that makes the .aspx page process an element and create a corresponding object on the server side. If a component is not running on the server, then it's not added to the page's control hierarchy.
var v = this.Form.TagName; //gets the name of the form that is maked as runat.
Of course if its not maked as runat then your code behind won't run anyway...
When you code in C# or Visual Basic in the code page, you will not have access to the object that do not have the runat=server option set.
You can easily access all the controls from a page using the me.controls page or something of the sort (I don't know the exact code but it's close to this) and check the type of the control to get the form.
Why do you need to know that? If a page does not have a runat=server form, it can't really be used as a server page.
You'd be able to access the form from the codebehind:
Response.Write(form1.Name);
Without the runat="server", you'd just get a compiler error.
I have an ASP.NET user control that contains a text box control and a button control. This user control will be added to my web-page many times. I need to have a piece of JavaScript that will run whenever the text box changes, and disable the button if the value of the text box is invalid. My question is this: how do I put JavaScript on the textbox that can reference only the button that is in the same user control? Remember, there are many ASP.NET user controls, each with a button and a text box, and I only want the invalid value in a text box to affect the one associated button. Thanks!
You can use ClientId property of controls (it's uniquely identifies control on the client side) and make something like that:
<asp:TextBox runat="server" ID="myTextBox" />
<asp:Button runat="server" ID="myButton" Text="click" />
<script language="javascript" type="text/javascript">
document.getElementById("<%=myTextBox.ClientID %>").onclick = function() {
document.getElementById("<%=myButton.ClientID %>").disabled = "disabled";
}
</script>
Also refer to this document:
Client Script in ASP.NET Web Pages, section Referencing Server Controls in Client Script