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:
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:
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:
If you wish to NOT treat warnings as errors, simply change the setting to false.