Quick MVC2 checkbox question - asp.net-mvc-2

Question

In order to get my EF4 EntityCollection to bind with check box values, I have to manually create the check boxes in a loop like so:
<p>
<%: Html.Label("Platforms") %><br />
<% for(var i = 0; i < Model.AllPlatforms.Count; ++i)
{ %>
<%: Model.AllPlatforms[i].Platform.Name %> <input type="checkbox" name="PlatformIDs" value="<%: Model.AllPlatforms[i].Platform.PlatformID %>" /><br />
<% } %>
</p>
It works, but it doesn't automatically populate the group of check boxes with existing values when I'm editing a model entity. Can I fudge it with something like?
<p>
<%: Html.Label("Platforms") %><br />
<% for(var i = 0; i < Model.AllPlatforms.Count; ++i)
{ %>
<%: Model.AllPlatforms[i].Platform.Name %> <input type="checkbox" name="PlatformIDs" value="<%: Model.AllPlatforms[i].Platform.PlatformID %>" checked=<%: Model.GameData.Platforms.Any(p => PlatformID == i) ? "true" : "false" %> /><br />
<% } %>
</p>
I figure there has to be something along those lines which will work, and am just wondering if I'm on the right track.
EDIT: I'm purposely staying away from MVC's check box HTML helper methods as they're too inflexible for my needs. My check boxes use integers as their values by design.

Answer 1

Close. You'll actually want to modify your server-side code so that the "checked" attribute is not emitted at all unless you want the checkbox to be checked.
checked="true"
or
checked="false"
are technically both invalid HTML. Source.
If you want a checked checkbox, you want to emit:
checked="checked"
Any value in the quotes will actually check the box (including checked="false"), but checked="checked" is considered proper.
So, updating your code, just tweak the ternary operator to use checked='checked' or nothing at all.
<%: Model.AllPlatforms[i].Platform.Name %> <input type="checkbox" name="PlatformIDs" value="<%: Model.AllPlatforms[i].Platform.PlatformID %>" <%: Model.GameData.Platforms.Any(p => p.PlatformID == i) ? "checked='checked'" : "" %> /><br />

Answer 2

You're on the right track, but I think you need to modify the snipet to it to
<%: Model.GameData.Platforms.Any(p => PlatformID == i) ? "checked='true'" : string.Empty %>