使用 Razor 的条件 HTML 属性

小开

I guess a little more convenient and structured way is to use Html helper. In your view it can be look like:

@{
var htmlAttr = new Dictionary<string, object>();
htmlAttr.Add("id", strElementId);
if (!CSSClass.IsEmpty())
{
htmlAttr.Add("class", strCSSClass);
}
}


@* ... *@


@Html.TextBox("somename", "", htmlAttr)

If this way will be useful for you i recommend to define dictionary htmlAttr in your model so your view doesn't need any @{ } logic blocks (be more clear).

小开

最佳答案

You didn't hear it from me, the PM for Razor, but in Razor 2 (Web Pages 2 and MVC 4) we'll have conditional attributes built into Razor (as of MVC 4 RC tested successfully), so you can write things like this:

<input type="text" id="@strElementID" class="@strCSSClass" />

If strCSSClass is null then the class attribute won't render at all.

What goes wrong with providing your own quotes

If you try to use some of the usual C# conventions for nested quotes, you'll end up with more quotes than you bargained for because Razor is trying to safely escape them. For example:

<button type="button" @(true ? "style=\"border:0px\"" : string.Empty)>

This should evaluate to <button type="button" style="border:0px"> but Razor escapes all output from C# and thus produces:

style=&quot;border:0px&quot;

You will only see this if you view the response over the network. If you use an HTML inspector, often you are actually seeing the DOM, not the raw HTML. Browsers parse HTML into the DOM, and the after-parsing DOM representation already has some niceties applied. In this case the Browser sees there aren't quotes around the attribute value, adds them:

style="&quot;border:0px&quot;"

But in the DOM inspector HTML character codes display properly so you actually see:

style=""border:0px""

In Chrome, if you right-click and select Edit HTML, it switch back so you can see those nasty HTML character codes, making it clear you have real outer quotes, and HTML encoded inner quotes.

So the problem with trying to do the quoting yourself is Razor escapes these.

If you want complete control of quotes

Use Html.Raw to prevent quote escaping:

<td @Html.Raw( someBoolean ? "rel='tooltip' data-container='.drillDown a'" : "" )>

Renders as:

<td rel='tooltip' title='Drilldown' data-container='.drillDown a'>

The above is perfectly safe because I'm not outputting any HTML from a variable. The only variable involved is the ternary condition. However, beware that this last technique might expose you to certain security problems if building strings from user supplied data. E.g. if you built an attribute from data fields that originated from user supplied data, use of Html.Raw means that string could contain a premature ending of the attribute and tag, then begin a script tag that does something on behalf of the currently logged in user(possibly different than the logged in user). Maybe you have a page with a list of all users pictures and you are setting a tooltip to be the username of each person, and one users named himself '/><script>$.post('changepassword.php?password=123')</script> and now any other user who views this page has their password instantly changed to a password that the malicious user knows.

使用 Razor 的条件 HTML 属性

Further Reading

What goes wrong with providing your own quotes

If you want complete control of quotes