MVC3视图中的条件逻辑是一种好的做法吗？

Question

Here's an example view, I use it to output every Category in my database. It's a recursive relationship, so a Category can have a List<Category> of Subcategories.

@model DSS.WebUI.Models.CategoriaModel

<div class="categories">
    <h3>
        @if (Model.Subcategorias.Count > 0)
        {
            <img src="http://i.imgur.com/t5UXT.gif" />   
            <a href="#">@Model.Nombre</a>
            <p class="subtext">@Model.Encabezado</p>
        }
        else
        {
            <a class="nochild" href="#">@Model.Nombre</a>
            <p class="subtext nochild">@Model.Encabezado</p>
        }
    </h3>
    <div>
        <ul>
            @Html.DisplayFor(x => x.Subcategorias)
        </ul>
    </div>    
</div>

Is conditional logic like this kosher? Or is it a code smell I should avoid and how?

Answer 1

This kind of conditional logic looks fine to me. Based on the number of sub-categories you have in your view model you are generating one or another html fragment. What would have been bad is to repeat this exact same condition with the same output in many places of your application. In this case you could externalize it into a partial or write a custom HTML helper.

Answer 2

I think it's better to implement your logic inside your controller instead of HTML codes, in these situation I try to do something like following :

    @if (ViewBag.SubCategoryHasData)
    {
        <img src="http://i.imgur.com/t5UXT.gif" />   
        <a href="#">@Model.Nombre</a>
        <p class="subtext">@Model.Encabezado</p>
    }
    else
    {
        <a class="nochild" href="#">@Model.Nombre</a>
        <p class="subtext nochild">@Model.Encabezado</p>
    }

and inside your action :

    ViewBag.SubCategoryHasData = Subcategorias.Count > 0;

hope this help.

Answer 3

The way you do it is fine.

Just two things to make sure your separation of concerns is ideal:

1. Use the IEnumerable.Any() as in

    Subcategorias.Any() 

   instad of

    Subcategorias.Count > 0; 

   This expresses your intent better and is in some cases faster (in some cases the Count needs to iterate over the whole list, while Any() needs to read only the first item).

2. Make sure your Model.Subcategorias is a plain List. If you have received the data from an Entity Framework model, this might be a lazily evaluated proxy and may cause a database call.