ASP.NET MVC Razor - lambda error

Question

I have an extension method

public static HelperResult List<T> (this IEnumerable<T> items, Func<T, HelperResult> template) {

            return new HelperResult(writer =>{
                foreach (var item in items)
                    template(item).WriteTo(writer);
            });

        }

When I try to use this method like this

  <ol>
     @Model.List(t=> {@<li>@t.Title</li>});
  </ol>

I get an error "; expected"

But if I do

<ol>
    @Model.List( @<li>@item.Title</li>)
   </ol>

it's OK. (what is the variable "item"? Where does it define?)

Why does the first example throws an error?

archil · Accepted Answer · 2011-09-26 12:22:32Z

3

The one solution is to declare razor helper like this

@helper ItemWriter(string item)
{
    <li>@item.Title</li>
}

And then pass this to your extension function

@Model.List(ItemWriter)

I know this code can be made better, but this works. Main idea is to use Razor Helpers

edited Sep 26, 2011 at 12:22

answered Apr 10, 2011 at 9:41

archil

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SLaks · Accepted Answer · 2011-04-10 14:15:45Z

2

The syntax @<tagname>...</tagname> declares a lambda expression that takes a parameter named item and returns a HelperResult.

You cannot use it as a statement; your first example cannot work.

answered Apr 10, 2011 at 14:15

SLaks

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1 Comment

SLaks Over a year ago

For the same reason that you cannot write x => "abc"; as a normal statement. There is no way to emit HTML as an embedded statement in Razor; you need to use it as a lambda.

hammett · Accepted Answer · 2011-06-29 03:36:54Z

1

That's pretty much the reason why I had to create Castle.Blade. It supports @=> p ... as an expression to create a lambda with named args. It also supports nesting these declarations, which razor doesn't.

answered Jun 29, 2011 at 3:36

hammett

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