I have an aspx document (I know nothing about asp, .net, aspx, nada). It is a normal html table structure for the most part, but there are strings of asp that seem to be inserting some sort of dynamic content. They are in the form:
<asp:Image ID="imgTopImage" runat="server" ImageUrl="~/Images/topbar.jpg" />
<asp:Label ID="lblStyleCaption" runat="server" CssClass="label_caption" Text="Theme: " Visible="false" />
<asp:DropDownList ID="dropStyles" Width="150" runat="server" AutoPostBack="true" />
It seems that whenever I delete one of these——something as innocuous as, say, the line with the asp:Image tag, which I would think should just remove the image, when I load the page I get run-time errors. It's very particular. My question is, is this compiled somehow, which is making it so fragile. Even just changing the topbar.jpg to something.png gives me an error. Do I need to track down the original files this was compiled from, or is this normal server-side asp(x?) that I'm just somehow else goofing up my changes to?
ASPX pages are compiled, and those tags refer to objects that are known to the server, so removing them could cause errors.
First, some basics in layman's terms
Tags that begin with ASP: (Example, <ASP:Button id="btnSubmit" runat="Server" Text="Click Me" />)
are not standard html buttons. They are server controls. When generating the html that goes out to the browser, the ASP.NET runtime looks at the server controls and creates the appropriate content depending on the browser visiting the page.
In the case of the Button control, it's usually a standard html button, but the runtime also generates the JavaScript and such to handle the button's server-side click event.
Why you're probably seeing errors when you remove a control:
Quite often, there's server-side code that's written that accesses these controls. For example, the developer may have decided to change the Text or the Visible property due to some event.
If this is the case, and you remove the <asp:Button> tag, then there will be server-side code that references an object that no longer exists in the aspx page, hence the errors.
More at these links on Server Controls:
http://www.w3schools.com/aspnet/aspnet_controls.asp
(Actually, this older one is better for a new-to-asp.net developer: http://msdn.microsoft.com/en-us/library/zsyt68f1(VS.71).aspx
http://support.microsoft.com/kb/306459
I'd also recommend taking some time watching basic videos or going through the tutorials at http://www.asp.net/get-started
I just noticed this in your question:
Even just changing the topbar.jpg to something.png gives me an error.
That is a bit odd, but I know of at least one way it could happen...
Generally, Visual Studio will give you a warning (and not an error) if you include a relative URL to an image or a linked page that doesn't exist. The warning shouldn't block you from compiling. However, Visual Studio does have a setting that tells it to treat warnings as errors. That will block it from compiling. Here's how that would be set up:
from Project Settings> Configuration Properties select the build
setting and change the “treat warnings as errors” settings to true.
If you wish to NOT treat warnings as errors, simply change the setting to false.
Related
There are quite a few questions out there regarding this (for me, recurring) issue, but none of them have solved my problem.
Problem:
Whatever control I add in my aspx page, it is not recognised in the codebehind. Compiling doesn't work, because the ID is not recognised.
None of the following worked:
Clean and rebuild solution.
Close and open VS
Delete asp.net temp files
Check project's target framework.
Check assemblies are all there.
Check designer viewn to see if the control is actually there (it is)
Get control's ID with JS function to check it is the intended one (it is)
The problem has started only recently. In fact, I can reference the older controls fine.
The problem is observed both with standard ASP controls and Telerik ones.
Does anyone know of something else I should try? Please help me, I'm in the middle of a project and this is causing unnecessary delays, ta.
Make sure all of your asp.net controls (in the .aspx file) have the:
runat='server'
tag... Without this, you will not be able to reference the controls.
e.g.
<asp:Label runat='server' Text='Test Label' ID='TestLabel' />
Hope this helped...
Rodit
This is how I solved my issue. For a full account of it, please refer to the comments above.
I've noticed that although my project was already of web application type, designer files weren't showing.
I've forced the designer files to be recompiled by clicking on the ''convert to web application' option
I was then able to reference the control ID.
Thanks to the commentators anyway.
I was having a similar issue, due to the fact that I was using the pre-generated Login page. My solution was to change this section from this:
<asp:Login runat="server" ViewStateMode="Disabled" RenderOuterTable="false">
<LayoutTemplate>
To this:
<asp:Login ID="asplogin" runat="server" ViewStateMode="Disabled" RenderOuterTable="false">
<LayoutTemplate>
basically, I just added an ID to the asp:Login which allowed me to access the objects in the code from behind by prefixing the control name with asplogin
asplogin.youControlNameHere
Climbing the learning curve for creating asp.net webform pages with Visual Studio 2010 (VB).
I had written a fairly complicated .aspx page with form controls, including textboxes and buttons, etc. I never thought to place the form controls inside a <form> block. Instead, all the controls include the "runat" directive; for example, <asp:textbox id="txtUserName" runat="server"> etc. In the codebehind I access the data with strUserName = txtUserName.text. This seems to work just fine.
Now, though, I received some form pages from our contracted "professional" web developer wherein the form code is all enclosed in a <form runat="server">block, and none of the controls include the runat directive. Accessing the data from these controls is a little different: It uses the <input type="text name="txtUserName" id="txtUserName" /> method, and accessing the data in the codebehind
is strUserName = Request.Form("txtUserName").ToString.
My method seems to work fine, but I am wondering if there is a difference in behavior or reliability between my method and his. Even though my way works, am I doing it wrong?
Mine is based on online research I have done to learn this stuff, and I don't remember seeing anything that looked like his. However, just today I see places that are saying that on .aspx pages, form controls MUST be enclosed in a <form> block (i.e., this page at w3schools.com).
Can anyone clarify this for me?
Thanks for your help!
You're not doing it incorrectly (you're using my preferred approach) but your inputs should still be in an enclosing Form tag.
He's using HtmlControls (System.Web.UI.HtmlControls namespace) and you're using web controls (System.Web.UI.WebControls.) Your controls provide better functionality on the server (viewstate and accessing via server code) and his approach is lighter weight.
Situation: I have been creating webpages in HTML5/CSS3 & Javascript using Sublime 2 text editor for a year, however a college course now requires me to use Asp.Net and Visual Studio 2010. I do not use the designer because I am proficient at doing things by hand, however I find that writing asp: inside every element is time consuming and causes syntax errors when applied to some HTML 5 tags and not others.
Example HTML 5: <button id="btn" type="submit" value="Button"/>
Example Asp.net: <asp:Button ID="Button1" runat="server" Text="Button" />
Question: Can the asp: portion be omitted without effecting anything or is it required for IIS or the C# back-end functionality? What about runat="server" can that be omitted?
Google has come up dry regarding my inquiry, so any help is appreciated.
you simply cannot remove either of the two
but hear me out why, because I have a feeling you are not familiar with ASP and therefor are mistaking the meaning of the asp: and the runat="server" syntax.
first: runat="server"
this property on an element, tells the the compiler that this is actually a server side control
so a <button/> is not the same as an <button runat="server"/>
the first one is pure html, while the second one is a control, which can be bound to on the server side. .Net will give it a clientID (not to be mistaken by the ID you have to give it yourself).
second: asp:
this is a prefix, on certain elements, that tells the compiler these are ASP controls (the default controls given by the ASP.net framework). These include Buttons, TextBoxes, DropDownLists, ...
do not mistake 1 of these with a html element.
an <asp:Button id="myAspButton" runat="server"/>
is not the same as a <button id="myHtmlButton"/>
the first, is a server side control, which can be bound to (see it's runat="server" attribute), and this control renders to the browser as a <input type="submit"/> for example.
you could alter the rendering of the asp.net button class to make it return something entirely differnt if you wish.
and you are also not limited to using asp.net classes.
you can create your own controls, and put them in a custom created library
you could give those your own prefix.
if I created such a custom control, I could register a prefix for it in the web.config file,
and thus I could create a custom button extending from the original one (but with a default label in front...
<myc:CustomButton ID="myButton" Text="myButton" Label="myLabel" runat="server"/>
which could render into:
<label>myLabel</label>
<button ID="*******">myButton</button>
the asterisks are symbolizing the Unique ID it will get from the .net framework
if you want to know more on custom controls, or extending default controls
here is a step by step explanation to create custom controls, or extend from a TextBox control.
it also shows how you add a custom prefix for your controls (in the this case 'cc')
you can find more info here
The runat="server" part is required to tell .NET that it will have to render a button there (which will contain .NET specific ID for processing upon POST). Not too familiar with web forms (I started with MVC), but I would assume that the asp: part is to help distinguish between server controls and standard HTML markup.
Why not try removing it and if it breaks something, then you know it's needed. For instance if the button doesn't show up after removing it, then obviously the .NET markup parser needs it to be there in order to know that it is a place holder for a server control.
when trying to translate the confirmation message to Norwegian i get the following error:
Cannot have more than one binding on property 'OnClientClick' on 'System.Web.UI.WebControls.LinkButton'. Ensure that this property is not bound through an implicit expression, for example, using meta:resourcekey.
i use Explicit localization in the following manner:
<asp:LinkButton ID="lnkMarkInvoiced" runat="server" OnClick="lnkMarkInvoiced_OnClick"
OnClientClick="<%# Resources: lnkMarkInvoicedResource.OnClientClick%>"
Visible="False" CssClass="stdtext" meta:resourcekey="lnkMarkInvoicedResource" ></asp:LinkButton>
here's the local resource file entry:
<data name="lnkMarkInvoicedResource.OnClientClick" xml:space="preserve">
<value>return confirm('Er du sikker?');</value>
if i remove the meta attribute i get the English text(default).
how do i get the Norwegian text appearing without resorting to using the code behind?
Update:
removing the meta attribute prevents the exception from occurring but the original problem still exists. I can't get the Norwegian text to show.
only the default English text shows.
Another Update:
I know this question is getting old but i still can't get the Norwegian text to display.
If anyone has some tips please post a response.
Looks like you're making the problem harder by inlining the onclick. Why not split it out to a separate line?
<script>
function markInvoiced()
{
return confirm('<%= Resources.SomehowGet.lnkMarkInvoicedResource.OnClientClick%>');
}
</script>
<asp:LinkButton ID="lnkMarkInvoiced" runat="server" OnClick="lnkMarkInvoiced_OnClick"
OnClientClick="return markInvoiced();"
Visible="False" CssClass="stdtext" meta:resourcekey="lnkMarkInvoicedResource" ></asp:LinkButton>
And while we're looking at your code, you realize that you're essentially building an <a> tag, right? As such, why not just build an <a> and save yourself some grief?
And finally, next project why not ditch the built-in ASP.NET localization nighmare in favor of something sane like FairlyLocal, in which case you'd write this:
<a href="#" onclick="return confirm(<%=_"really?"%>) onserverclick="lnkMarkInvoiced_OnClick" runat="server">
<%=_("Mark Invoice")%>
</a>
Are you using the .NET resource manager and satellite assemblies to store your localized resources? It looks like you have hard-coded the alternative language in your markup, rather than storing it in a language-specific resources assembly...
.NET has some extremely rich localization and globalization capabilities. If you use them properly, localization should be a pretty automatic thing (assuming your client is providing their language code as part of the HTTP headers). Even if your client has not configured their browser with the appropriate language, it is still easy enough to manually change the UI culture via a user request (clicking a flag icon, configuring a setting, etc.)
This article might be helpful: ASP.NET Web Page Resources Overview
That meta tag is using implicit localization when you're using explicit localization in the OnClientClick. You will need to choose one method or the other. If you are to use explicit localization, you'll need to do the necessary work to set the proper culture info in your application in the code-behind.
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.