My thought is for performance reasons. You can have a control that is not runat="server", and it will not be included for server side processing. For example if you have a static label that will never change text, or something like that.

Posted by Jeremy on Jan 16, 2008 at 08:20 AM UTC - 5 hrs

The problem with that theory is that if you neglect to put the runat="server" in the asp:Label it will compile and run, but it doesn't show up in the page (only the verbatim code, which of course is enclosed in angled brackets, so it doesn't show on the page.)

I guess it's possible to want to use a tag like that in your xml, but I wouldn't call it likely. I wonder if anyone has /ever/ done so.

Posted by Sammy Larbi on Jan 16, 2008 at 09:01 AM UTC - 5 hrs

To be consistent. :)

You can create your own server tags with your own namespace and tag name (such as myLib:NewLabel). Since ASP.NET can't make any assumptions about what is an HTML (or XML) tag, and what is an ASP.NET control you have to tell it.

Also, if I'm not mistaken, you can attribute any HTML tag with runat, and it will create an html element object so you can manipulate it in code. (wooo...)

So, if the asp.net controls didn't follow the same pattern it wouldn't be consistent, because they are implemented the same way as you'd implement your own server controls after all.

At least that's the way I see it.

A comment about your "Object obj = new Object()" comment:
That's because when you declare "Object obj" you're actually declaring a reference to an object of type Object, not really an instance of type Object. Initially it doesn't reference anything (similar to pointers).

Posted by Glitch on Jan 16, 2008 at 11:49 AM UTC - 5 hrs

@Glitch: I was hoping you'd respond.

You are right - it does allow it in an HTML tag (as I meant to get across when I said "For normal HTML elements, I understand the necessity of using the attribute when you want that element to be tied to the server.")

If consistency is the case, (and that is a valid reason I didn't think of) then I wonder why they didn't make you type runat="browser" for the controls that shouldn't run on the server (minus html elements, which should require runat="server" to run there).

I'm being nitpicky, I realize, but it's just been annoying me to have to alt-tab from browser to IDE, enter runat=server in the appropriate spot, hit alt-tab back to browser, and reload, waiting for the recompilation. =)

I'll get used to it and fall in line soon enough.

As for telling the compiler several times what you want (Object obj = new Object()) - I'd prefer type inference to short-term memory loss. Nothing against C# of course - just poking a little fun at the entire lot of languages in the same tradition. =)

Posted by Sammy Larbi on Jan 16, 2008 at 12:24 PM UTC - 5 hrs

How though, would they know what was not an html element, and what was? If I'm not mistaken, modern pages are verified using XHTML which follows the XML spec right? Which I would imagine means you can use namespace prefixes within your XHTML code. So if that's true, you couldn't assume any prefix was guaranteed to be a control only prefix.

Granted, by importing your controls it would know what tag prefixes would be mapped to .NET namespaces, but what happend if your tag prefix collided with a legit XHTML namespace prefix? (I appologize too if my terminology is wrong, I'm not savvy with XML namespaces and such.)

If then a control wasn't found should it error? Or should it just let the control be rendered as-is?

I think, as annoying as it is, supplying the runat="server" allows the .NET parser a more efficient method for determining what tags are controls and what ones aren't. If you runat="server" and a valid .NET implementation isn't found, it's obviously an error. If you don't runat="server", no time is wasted looking at the tag (aside from what is needed that is). :) It sure beats adding runat="client" for all of your non-control tags which probably outnumber control tags significantly.

But I feel your pain. I haven't done a lot of ASP.NET work, but almost every time I do I forget the runat and bang my head on the desk for a minute or two before sighing and realizing my error.

Posted by Glitch on Jan 18, 2008 at 09:55 PM UTC - 5 hrs

You are right. I guess I'm coming from the "opinionated framework" stance where I think they should just treat the asp namespace as their own, and run it automatically.

If someone is using that namespace AND ASP.NET, they are probably crazy. I don't think you should disallow it because it's crazy, however. I think you should do it to make it easier on all the sane folks. =)

Posted by Sammy Larbi on Jan 21, 2008 at 09:15 AM UTC - 5 hrs