"if" considered harmful in ASP.NET MVC View (.aspx) files?

Question

I remember seeing a blog (or something) that said you should not use <% if ... %> in .aspx files in ASP.NET MVC, but I can't remember what it said the alternative is. Can anyone remember seeing this and point me to it?

Answer 1

I feel that is just fine. It allows for the view to have control of its presentation.

Answer 2

I suspect that the point was an attempt to avoid spaghetti code rather than restrict the use of "if"s, here is a link to a Rob Conery blog about this, he does actually mention using helpers instead of Ifs so this may be what you saw ASP.NET MVC: Avoiding Tag Soup

Answer 3

I'm not sure if this is what you saw, but here is a blog that mentions it. See item #11.

Answer 4

I think what you're referring to is a post by Rob Conery, where he mentions a rule he uses:

If there's an if, make a helper

So to answer your question, the idea is that if you find yourself needing to use if in your View, you should consider adding a helper extension method to render that part of your View instead.

Answer 5

Is this the issue you're referring to?

binding expressions can not be used in statement block <% %>, just as statements can not be used in a binding expression block <%# %>

-- bruce (sqlwork.com)

"Jason" <> wrote in message news:23C11F83-A2AA-406D-BDEC-...

What is wrong with the following if statement in my aspx page?

<%If #DataBinder.Eval(Container.DataItem, "locationType") <> "T" Then%>

I get error that says: BC30201: Expression expected.

Bruce Barker

Answer 6

Basically what it means is that you shouldn't have huge if statements in your Views, your Controllers and ViewModels should be able to handle the logic. Example:

<h2 class="title">
    <% if (ViewData["category"] == null { %>
        All Products
    <% } else { % >
        <%= ViewData["category"] %>
    <% } %>
</h2>

Should be:

<h2 class="title>
    <%= Model.Title %>
</h2>

If your controllers and ViewModels can't handle the logic, you should write Html Helpers for more complicated logic (thus making it reusable and more readable).

<h2 class="title>
    <%= Html.GetPageTitle(Model.Category) %>
</h2>

Answer 7

As i think the best approach for this is try to handle your if condition in controller and pass the specific view for required result or pass the View name in a variable to render.

public class HomeController :Controller
{
    public ActionResult Category(string? category)
    {
       View viewToReturn;
       if (category == null)
          viewToReturn = View("CategoryList", repo.GetAllCategory); /// it is a View
       else
          viewToReturn = View("Category", repo.GetCategory(category)); /// it is a View

       return viewToReturn;
    }
}

Well, Martin answer is also from best practices.

Answer 8

So if I have say a list of customers and I'm going to display basically a contact card for each and if they have paid the background of the div is green and if they haven't the background is red. In this case you guys are suggesting I create a helper that would out put the div with the proper background based on say a HasPaid bool in the model object?

This makes sense to me. I got really confused when I read a blog post yesterday saying if you wanted CSS like to change like that it should come from your controller. My gut reaction was that he was on crack, but being new I didn't want to dismiss him outright. That gut reaction has bitten me in the past :)