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.
Related
Should I use ASP elements with a runat="server" attribute or an HTML form?
It seems like using ASP tags such as <asp:TextBox> is much more comfortable since I don't have to redirect the user to another page on a form submition, but also from what I've seen, it seemed like HTML forms are the more accepted way. I was starting to wonder if using ASP elements increases server load or has any other disadvantage?
In case I should use ASP elements, how do I validate the input with Javascript before sending it to the server?
In case I should use HTML forms, how do I not redirect the user on submition and also not run the server code on page load?
You can easily use the HTML5 input type in Web Forms by adding the runat="server" attribute, so that it can be accessed on the server-side:
<label for="name">Name:</label>
<input type="text" id="name" name="name" required
minlength="4" maxlength="8" size="10" runat="server">
Note, on the server-side you will access it via the Value property of the input element, not with the Text property of a typical ASP.NET textbox control.
Contrary to what a lot of people think, ViewState only ever becomes a problem when people do silly things like nesting data-bound controls, in which case it can become bloated very quickly.
Not sure what you're asking regarding validation... but you still have options like this on both client and server. If you're working with an existing Web Forms project, I would stick with regular ASP.NET controls and keep it simple. This way, you can have out-of-the-box validation on both client and server.
We're working with a third party system and we need to modify some ASP.Net controls so that they have a specific token added to their HTML id attribute (so the third party system can identify them from the request), as well as HTML comments before and after the controls' output.
Basically, we need to be able to take say a TextBox (say for "Employee First Name") and dynamically change its output to something like this:
<!-- FIZZBOT_START -->
<input id="EmployeeFirstName_FIZZBOT_" ... />
<!-- FIZZBOT_END -->
We would ideally like to implement this so that the developers only have to do something like this:
<xxx:FizzbotWrapper ID="MyWrapper" runat="server">
<asp:TextBox ID="EmployeeFirstName" runat="server" />
</xxx:FizzbotWrapper>
Is there any way to get such an interface to produce such output, while still being able to:
maintain control state across requests
work properly with Validators
work properly with UpdatePanels
allow developers to refer to the original ID in the codebehind for readability (instead of having to refer to "EmployeeFirstName_FIZZBOT_"
work with out-of-the box ASP.Net controls like TextBox and not just controls we've derived.
I've tried a few ways of doing this (the technique that was the most promising was this, but I ran into some trouble getting it to work with validators, and it wouldn't work at all with controls we don't have the source code to).
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.
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.
I like HtmlControls because there is no HTML magic going on... the asp source looks similar to what the client sees.
I can't argue with the utility of GridView, Repeater, CheckBoxLists, etc, so I use them when I need that functionality.
Also, it looks weird to have code that mixes and matches:
<asp:Button id='btnOK' runat='server' Text='OK' />
<input id='btnCancel' runat='server' type='button' value='Cancel' />
(The above case in the event you wanted to bind a server-side event listener to OK but Cancel just runs a javascript that hides the current div)
Is there some definitive style guide out there? Should HtmlControls just be avoided?
It might be useful to think of HTML controls as an option when you want more control over the mark up that ends up getting emitted by your page. More control in the sense that you want EVERY browser to see exactly the same markup.
If you create System.Web.UI.HtmlControls like:
<input id='btnCancel' runat='server' type='button' value='Cancel' />
Then you know what kind of code is going to be emitted. Even though most of the time:
<asp:Button id='btnCancel' runat='server' Text='Cancel' />
will end up being the same markup. The same markup is not always emitted for all WebControls. Many WebControls have built in adaptive rendering that will render different HTML based on the browser user agent. As an example a DataGrid will look quite different in a mobile browser than it will in a desktop browser.
Using WebControls as opposed to HtmlControls also lets you take advantage of ASP.NET v2.0 ControlAdapters which I believe only works with WebControls, this will allow you programatic config driven control over the markup that gets emitted.
This might seem more valuable when you consider that certain mobile browsers or WebTVs are going to want WML or completely different sets of markups.
In my experience, there's very little difference. As Darren said, if you don't need server-side functionality, HTML controls are probably lower-impact.
And don't forget, you can bolt server-side functionality onto almost any HTML control just by adding a runat="server" directive and an ID to it.
well... i wouldn't use an html control if you don't need to do anything on it on the server. i would do
<input id='btnCancel' type='button' value='Cancel' />
fin.
By adding runat="server" you can get access to any HTML controls in server side..
and I believe HTML controls are less weight compared to ASP.NET server controls..