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

Question

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.

Houstonhoustonia

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... – Mclendon

You make like #6982353 – Traylor

Please vote here. – Hepatitis

Related: https://mcmap.net/q/81040/-asp-net-mvc-razor-ternary – Smacker

Answer 1

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

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

Krystenkrystin

Here's a handy reference to Razor syntax: C# Razor Syntax Quick Reference – Brocky

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

Can I add && operator into this logics ? – Ronn

also possible: <a class="btn btn-secondary @(item.ValidTo == null ? "disabled-button" : "")">Link</a> – Fosdick

Answer 2

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).

Cabe

just noticed your addendum after adding the similar comments to the main answer. – Complemental

How is an expression a generic method? – Minnesinger

Answer 3

A simpler version, for easy eyes!

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

Gpo

that's not simpler. that's the same answer with different values – Javierjavler

-1 Dave Rael is right, this is the same code with different values – Cuprous

This actually explain the ternary operator. So it's a good addiction to the solution that doesn't say where is the true and false in the condition. – Ripp

I thought so. as developers we are allowed to have clear answers.. sometimes. – Gpo

I find this answer much clearer to me. Thanks @MonstersX – Expert

Answer 4

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.

Vyner

Answer 5

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")

Smallwood

Answer 6

You can also use this method:

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

Try this .. Good luck Thanks.

Caecum

is there any need for adding @ with mvc condition? I don't think so, because @ has already been used at the start. – Chapin

Answer 7

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")">

Debus