Conditionally displaying parts of my view

Question

Say I have an asp.net mvc website with a page that lists products. ON that page I have a "delete" button that should only show up for the user that inserted the product. What's the best way to do this?

One way I thought of doing it was setting a boolean in the controller to let the view know if the button should be displayed. Something like:

if(IsProductOwner(UserId))
    ViewData["CanDelete"] = true;

Then in the view I can just do

<% if((boolean)ViewData["CanDelete"] == true) { %>
    // show delete button
<% } %>

But is there a better way to do this?

Answer 1

My initial thought is that you should at least make that a function of the Product class so you can go:

<% if (product.IsOwnedBy(UserId)) { %>
    // show delete button
<% } %>

This removes some of the floaty ViewData and builds the business logic into your classes rather than floating out on the edges.

However, I haven't found a decent way to do this sort of conditional display in views unless the view is significantly different then I get the action to display a different view depending on the context.

Answer 2

MVC is about separating business logic from presentation. The answer provided by Garry looks dirty (and non-performant) from that aspect. You can instead use strongly typed ViewData and more common data points to achieve the same. e.g. Instead of ViewData["CanDelete"] you can use ViewData.IsOwned and use that variable around on more than one occasion, avoiding variable inflation. So your business code becomes:

ViewData.IsOwnedByThisUser = product.IsOwnedBy(currentUserId);

And your view code becomes:

<% if(ViewData.IsOwnedByThisUser) { %>
// show delete button
<% } %>

You can use same variable for "edit" buttons as well.

The difference in this approach is you completely detach view presentation from your business logic. Your business logic can change (and your controller can adapt to it) but you don't ever need to change your view code, unless your application design goes under a significant change.