How to use ternary operator in razor (specifically on HTML attributes)?

433
votes

With the WebForms view engine, I'll commonly use the ternary operator for very simple conditionals, especially within HTML attributes. For example:

<a class="<%=User.Identity.IsAuthenticated ? "auth" : "anon" %>">My link here</a>

The above code will give the <a> tag a class of auth or anon depending on whether the user is authenticated.

What is the equivalent syntax with the Razor view engine? Because Razor requires HTML tags to "know" when to jump in and out of code and markup, I'm currently stuck with the following:

@if(User.Identity.IsAuthenticated)  { <a class="auth">My link here</a> }
else { <a class="anon">My link here</a> }

This is, to put it mildly, terrible.

I would love to do something like this, but am struggling to understand how in Razor:

<a class="@=User.Identity.IsAuthenticated ? "auth" : "anon";">My link here</a>

--

Update:

In the meantime, I've created this HtmlHelper:

public static MvcHtmlString Conditional(this HtmlHelper html, Boolean condition, String ifTrue, String ifFalse)
{
  return MvcHtmlString.Create(condition ? ifTrue : ifFalse);
}

which can be called like this from Razor:

<a class="@Html.Conditional(User.Identity.IsAuthenticated, "auth", "anon")">My link here</a>

Still, I am hoping there's a way to use the ternary operator without falling back to wrapping it in an extension method.

7
razorasp.net-mvc-3
Just as a matter of "Best Practice" I believe you should be returning type IHtmlString with the method new HtmlString("Some stuff here"); for helpers etc... – Justin Soliz
You make like stackoverflow.com/questions/6981853/… – Elan Hasson
Please vote here. – Shimmy Weitzhandler
Related: stackoverflow.com/questions/7729024/asp-net-mvc-razor-ternary – Nathan Hartley

7 Answers

820
votes

You should be able to use the @() expression syntax:

<a class="@(User.Identity.IsAuthenticated ? "auth" : "anon")">My link here</a>
64
votes

Addendum:

The important concept is that you are evaluating an expression in your Razor code. The best way to do this (if, for example, you are in a foreach loop) is using a generic method.

The syntax for calling a generic method in Razor is:

@(expression)

In this case, the expression is:

User.Identity.IsAuthenticated ? "auth" : "anon"

Therefore, the solution is:

@(User.Identity.IsAuthenticated ? "auth" : "anon")

This code can be used anywhere in Razor, not just for an html attribute.

See @Kyralessa 's comment for C# Razor Syntax Quick Reference (Phil Haack's blog).

28
votes

A simpler version, for easy eyes!

@(true?"yes":"no")
18
votes

For those of you who use ASP.net with VB razor the ternary operator is also possible.

It must be, as well, inside a razor expression: 

@(Razor_Expression)

and the ternary operator works as follows:

If(BooleanTestExpression, "TruePart", "FalsePart")

The same code example shown here with VB razor looks like this: 

<a class="@(If(User.Identity.IsAuthenticated, "auth", "anon"))">My link here</a>

Note: when writing a TextExpression remember that Boolean symbols are not the same between C# and VB.

3
votes

in my problem I want the text of anchor <a>text</a> inside my view to be based on some value and that text is retrieved form App string Resources

so, this @() is the solution 

<a href='#'>
      @(Model.ID == 0 ? Resource_en.Back : Resource_en.Department_View_DescartChanges)
</a>

if the text is not from App string Resources use this

@(Model.ID == 0 ? "Back" :"Descart Changes")
0
votes

You can also use this method:

<input type="text" class="@(@mvccondition ? "true-class" : "false-class")">

Try this .. Good luck Thanks.

0
votes

I have a field named IsActive in table rows that's True when an item has been deleted. This code applies a CSS class named strikethrough only to deleted items. You can see how it uses the C# Ternary Operator:

<tr class="@(@businesstypes.IsActive ? "" : "strikethrough")">