Generating HTML from server-side block in ASP.NET MVC

Question

This is a very newbie kind of ASP.NET question: I simply don't know and can't work out the correct syntax to use.

In my view I want to generate an action link if a certain condition is true on my model. I know how to generate a link using this syntax:

<%: Html.ActionLink("Do Something", "DoSomething", new { id = Model.ID }) %>

But for some reason that syntax doesn't work in this code:

<%
  if (Model.CanDoSomething)
    Html.ActionLink("Do Something", "DoSomething", new { id = Model.ID });
%>

I really am a newbie to ASP.NET, so I don't even know what the semantic name is for the different syntaxes <% and <%:; all I can tell is that <% is to void as <%: is to string. And clearly executing a line of code that just returns a string (Html.ActionLink()) is not going to have any effect. But what, pray what is the correct method to make my page render the action link?

It's a great pity I can't Google on "<%"! Any links or explanations of this subject will also be much appreciated.

DanielB · Accepted Answer · 2011-06-06 16:10:23Z

1

This will do the trick

<% if (Model.CanDoSomething) { %>
   <%: Html.ActionLink("Do Something", "DoSomething", new { id = Model.ID }) %>
<% } %>

<%: writes to the output buffer but encodes the string. You could also use <%= for unencoded output because ActionLink returns an encoded MvcHtmlString.

EDIT: This may also work

<%
  if (Model.CanDoSomething)
    Response.Write(Html.ActionLink("Do Something", "DoSomething", new { id = Model.ID }));
%>

edited Jun 6, 2011 at 16:10

answered Jun 6, 2011 at 16:04

DanielB

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4 Comments

Shaul Behr Over a year ago

Sure it would, and I worked that out myself. But surely there's a more elegant way of handling this kind of situation?

Max Over a year ago

@Shaul. Yes. Using Razor view engine instead. :)

DanielB Over a year ago

You can switch to MVC 3 with Razor view engine. This one has a far more intuitive syntax.

Shaul Behr Over a year ago

Ah, just saw your edit with Response.Write. That's exactly what I was looking for, thanks!

Adam Tuliper · Accepted Answer · 2011-06-06 16:24:20Z

1

<% - this by itself has no output. You would include code with no output in this block such as an if statement. If you want output - you must use it in conjunction with <%=
The difference with the : is that <%: means it will output to the response stream, not = required however the : means the output will be htmlencoded.

<%:"sometest&text" %>   //will emit "sometesttext" on the page.. htmlencoded.
<%="sometest&text" %> //will give you the same result without the '&' htmlencoded
<% SomeFunction() %> //will just run that function - there is no output
//you want
<%if (Model.CanDoSomething){%>
    <%:Html.ActionLink("Do Something", "DoSomething", new { id = Model.ID })%>
<%}%>

answered Jun 6, 2011 at 16:24

Adam Tuliper

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2 Comments

Shaul Behr Over a year ago

+1 for the explanation, if not exactly the solution I was looking for - thanks!

Adam Tuliper Over a year ago

thanks : ) how did it differ? Personally - I wouldn't use the Response.Write syntax. Its going to be a tad more work if you refactor going to razor syntax. There is also no need to use the htmlencoding colon syntax there either, since <%: HtmlEncodes, and the ActionLink helper already spits out type MvcHtmlString which says 'don't encode me'

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