For HTML 4, the answer is technically:
ID and NAME tokens must begin with a letter ([A-Za-z]) and may be followed by any number of letters, digits ([0-9]), hyphens ("-"), underscores ("_"), colons (":"), and periods (".").
HTML 5 is even more permissive, saying only that an id must contain at least one character and may not contain any space characters.
The id attribute is case sensitive in XHTML.
As a purely practical matter, you may want to avoid certain characters. Periods, colons and '#' have special meaning in CSS selectors, so you will have to escape those characters using a backslash in CSS or a double backslash in a selector string passed to jQuery. Think about how often you will have to escape a character in your stylesheets or code before you go crazy with periods and colons in ids.
For example, the HTML declaration <div id="first.name"></div>
is valid. You can select that element in CSS as #first\.name
and in jQuery like so: $('#first\\.name').
But if you forget the backslash, $('#first.name')
, you will have a perfectly valid selector looking for an element with id first
and also having class name
. This is a bug that is easy to overlook. You might be happier in the long run choosing the id first-name
(a hyphen rather than a period), instead.
You can simplify your development tasks by strictly sticking to a naming convention. For example, if you limit yourself entirely to lower-case characters and always separate words with either hyphens or underscores (but not both, pick one and never use the other), then you have an easy-to-remember pattern. You will never wonder "was it firstName
or FirstName
?" because you will always know that you should type first_name
. Prefer camel case? Then limit yourself to that, no hyphens or underscores, and always, consistently use either upper-case or lower-case for the first character, don't mix them.
A now very obscure problem was that at least one browser, Netscape 6, incorrectly treated id attribute values as case-sensitive. That meant that if you had typed id="firstName"
in your HTML (lower-case 'f') and #FirstName { color: red }
in your CSS (upper-case 'F'), that buggy browser would have failed to set the element's color to red. At the time of this edit, April 2015, I hope you aren't being asked to support Netscape 6. Consider this a historical footnote.
Here is a mostly clean attribute-based solution to the multiple submit button issue based heavily on the post and comments from Maarten Balliauw.
[AttributeUsage(AttributeTargets.Method, AllowMultiple = false, Inherited = true)]
public class MultipleButtonAttribute : ActionNameSelectorAttribute
{
public string Name { get; set; }
public string Argument { get; set; }
public override bool IsValidName(ControllerContext controllerContext, string actionName, MethodInfo methodInfo)
{
var isValidName = false;
var keyValue = string.Format("{0}:{1}", Name, Argument);
var value = controllerContext.Controller.ValueProvider.GetValue(keyValue);
if (value != null)
{
controllerContext.Controller.ControllerContext.RouteData.Values[Name] = Argument;
isValidName = true;
}
return isValidName;
}
}
razor:
<form action="" method="post">
<input type="submit" value="Save" name="action:Save" />
<input type="submit" value="Cancel" name="action:Cancel" />
</form>
and controller:
[HttpPost]
[MultipleButton(Name = "action", Argument = "Save")]
public ActionResult Save(MessageModel mm) { ... }
[HttpPost]
[MultipleButton(Name = "action", Argument = "Cancel")]
public ActionResult Cancel(MessageModel mm) { ... }
Update: Razor pages looks to provide the same functionality out of the box. For new development, it may be preferable.
Best Answer
The primary reason you don't use
<a>
tags directly is that you don't want to hardcode URLs in your application. TheHtml.ActionLink
method will abstract away the URL generation and you'll specify the controller, action, and other parameters.So, basically, the two lines you posted in your question are not really equivalent. You should consider adding the dynamic URL generation code to the
<a>
tag to make them functionally equivalent. Beside that, if you output HTML directly, you'll have to be extremely careful about HTML encoding stuff.Html.ActionLink
will do this job for you too.