How to use ? : if statements with Razor and inline

问题:

I'm updating my old .aspx views with the new Razore view engine. I have a bunch of places where I have code like this:

<span class="vote-up<%= puzzle.UserVote == VoteType.Up ? "-selected" : "" %>">Vote Up</span>

Ideally I'd like to do this:

<span class="vote-up@{puzzle.UserVote == VoteType.Up ? "-selected" : ""}">Vote Up</span>

However there's two problems here:

1. vote-up@{puzzle.UserVote .... is not treating the @ symbol as a start of a code block
2. @puzzle.UserVote == VoteType.Up looks at the first part @puzzle.UserVote as if it's supposed to render the value of the variable.

Anyone know how to address these issues?

回答1:

This should work:

<span class="vote-up@(puzzle.UserVote == VoteType.Up ? "-selected" : "")">Vote Up</span>

回答2:

The key is to encapsulate the expression in parentheses after the @ delimiter. You can make any compound expression work this way.

回答3:

@( condition ? "true" : "false" )

回答4:

In most cases the solution of CD.. will work perfectly fine. However I had a bit more twisted situation:

 @(String.IsNullOrEmpty(Model.MaidenName) ? " " : Model.MaidenName)

This would print me " " in my page, respectively generate the source  . Now there is a function Html.Raw(" ") which is supposed to let you write source code, except in this constellation it throws a compiler error:

Compiler Error Message: CS0173: Type of conditional expression cannot be determined because there is no implicit conversion between 'System.Web.IHtmlString' and 'string'

So I ended up writing a statement like the following, which is less nice but works even in my case:

@if (String.IsNullOrEmpty(Model.MaidenName)) { @Html.Raw(" ") } else { @Model.MaidenName } 

Note: interesting thing is, once you are inside the curly brace, you have to restart a Razor block.